HyperThreading
Hello, I'm running FreeBSD 7.2-RELEASE on a dual-core Xeon. It has a custom compiled SMP kernel, ACPI enabled, with the ULE scheduler. I've been looking into HyperThreading, and I've come to the conclusion that I should not use it. I've been told that HTT is disabled by default, however sysctl and dmesg seems to contradict that: CPU: Intel(R) Xeon(TM) CPU 2.40GHz (2395.93-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf29 Stepping = 9 Features=0xbfebfbff Features2=0x4400 Logical CPUs per core: 2 FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP/HT): APIC ID: 1 cpu2 (AP): APIC ID: 2 cpu3 (AP/HT): APIC ID: 3 cpu0: on acpi0 cpu1: on acpi0 cpu2: on acpi0 cpu3: on acpi0 SMP: AP CPU #2 Launched! SMP: AP CPU #3 Launched! SMP: AP CPU #1 Launched! machdep.hyperthreading_allowed: 1 hw.ncpu: 4 kern.smp.disabled: 0 kern.smp.active: 1 Am I correct to assume that the above means that HTT is enabled? There is nothing in my loader.conf, sysctl.conf, or kernel config file related to hyperthreading. Thanks. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Hyperthreading question
Hi all, I'm upgrading some machines from 4.8-RELEASE to 4.10-RELEASE. The machines in question are dual-processor xeon boxes. Now, my boss is adamant in that he doesn't want hyperthreading enabled on the machines. In 4.8-RELEASE things were simple... I just didn't add the "options HTT" line to my kernel config file. In 4.10-RELEASE though, HTT is enabled by default. So, is there any way to shut off the hyperthreading? I've tried disabling it in the BIOS, and had no luck whatsoever. Thanks, DMK PS: A direct reply would be welcome. I'm not subscribed to the mailing list. ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Disabling Hyperthreading...
Hi, I have installed FreeBSD 5.4 on Dell PowerEdge 1750, which has Xeon processors. I have recompiled the kernel with SMP support(should I add any option in Kernelconf file to disable it) When using top command I c 0123, processor it seems hyper threading is enabled. How do I disable it, or is it diabled Thanx for any advise. Cheers, Deepak Naidu. ___ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Hyperthreading Issues
Hi. It seems to me (From the limited knowledge that I have!) that my machine is not hyperthreading. I have done the following. 1. Ensured that the capability is enabled in the BIOS. 2. FreeBSD recongizes the capaiblity CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (1866.74-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf29 Stepping = 9 Features=0xbfebfbff Features2=0x4400> Logical CPUs per core: 2 real memory = 1073676288 (1023 MB) avail memory = 1033097216 (985 MB) ACPI APIC Table: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 3. The kernel is built for SMP # SMP -- Generic kernel configuration file for FreeBSD/i386 SMP #Use this for multi-processor machines # # $FreeBSD: src/sys/i386/conf/SMP,v 1.5.6.1 2005/09/18 03:37:58 scottl Exp $ include GENERIC1 ident SMP-CUSTOM # To make an SMP kernel, the next line is needed options SMP # Symmetric MultiProcessor Kernel device atapicam 4. In the past top would show the 2 different logical CPUs working however, this is not the case anymore. Can anyone help we with this issue. I am using 6.2 release. Thanks in advance. Derrick ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: HyperThreading
On Wed, 2009-05-06 at 02:20 -0400, APseudoUtopia wrote: > Am I correct to assume that the above means that HTT is enabled? > There is nothing in my loader.conf, sysctl.conf, or kernel config file > related to hyperthreading. Yes, you are correct. Try: % sudo ps gauxww Or % sudo top You can see the currently assigned CPU for each proc/thread. ~BAS ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Hyperthreading hurts 5.3?
summary: should I disable hypertheading in the BIOS when running 5.3? Background info: I have a new Dell Dimension 3000 running 5.3. I noticed some huge pauses when copying a large # of files across the network. Googling around found some information about earlier versions of 5.x and Hyperthreading being detrimenatl for performance. Whether or not it was the source of the network copy problem, I am trying to decide if I should disable Hyperthreading. Iif YES, I wasn't clear if people meant "disable in BIOS" or just some configuration setting in a *.conf file. (disabling HT will apparently mean I have to reinstall XP on the other drive. Not necessarily a bad thing, as it is supposedly also the way to solve the problem of my modem causing a BSOD in XP) thanks TjL ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading question
On Tue, Jun 08, 2004 at 03:36:28PM -0400, Dwayne MacKinnon wrote: : : I'm upgrading some machines from 4.8-RELEASE to 4.10-RELEASE. The : machines in question are dual-processor xeon boxes. Now, my boss is : adamant in that he doesn't want hyperthreading enabled on the machines. : : In 4.8-RELEASE things were simple... I just didn't add the "options HTT" : line to my kernel config file. In 4.10-RELEASE though, HTT is enabled by : default. : : So, is there any way to shut off the hyperthreading? I've tried : disabling it in the BIOS, and had no luck whatsoever. Hyperthreading is built into the kernel by default starting with FreeBSD-4.9. However, it is not enabled by default. To do so, do a "sysctl machdep.hlt_logical_cpus=0" ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
SMP vs. Hyperthreading?
Hi,
I've got a machine with a P4 that supports HTT (Hyperthreading) so I
thought about setting up a SMP-kernel.
Under 4.9 it seems to work (see excerpts from /var/log/messages
below), whereas on the same exact hardware under 5.2.1 I don't see two
virtual CPUs working.
For a first check I've run "cpuburn" (i.e. burnP6). Under 4.9 with one
"cpuburn" process active "top" etc. show a cpu-load of about 50% which
for me means SMP/HTT is active.
Under 5.2.1 it's a different story though: /var/log/messages shows
that there are 2 CPUs but the message indicating the second CPU has
been launched is missing ("/kernel: SMP: AP CPU #1 Launched!"). When I
run a "cpuburn"-Test under 5.2.1 CPU load indicated by "top" shows
100% so I assume SMP/HTT is not active.
So my primary question is - how do I get SMP running under 5.2.1 with
a hyperthreading-capable P4??
Thanks much in advance for any clue,
-ewald
-- < Cut here > --
Excerpt from /var/log/messages - 4.9:
Mar 12 15:00:30 mybox /kernel: CPU: Intel(R) Pentium(R) 4 CPU 2.60GHz (2593.68-MHz
686-class CPU)
Mar 12 15:00:30 mybox /kernel: Origin = "GenuineIntel" Id = 0xf29 Stepping = 9
Mar 12 15:00:30 mybox /kernel:
Features=0xbfebfbff
Mar 12 15:00:30 mybox /kernel: Hyperthreading: 2 logical CPUs
Mar 12 15:00:30 mybox /kernel: real memory = 394264576 (385024K bytes)
Mar 12 15:00:30 mybox /kernel: avail memory = 377823232 (368968K bytes)
Mar 12 15:00:30 mybox /kernel: Changing APIC ID for IO APIC #0 from 1 to 2 in MP table
Mar 12 15:00:30 mybox /kernel: APIC_IO: MP table broken: 8259->APIC entry missing!
Mar 12 15:00:30 mybox /kernel: Changing APIC ID for IO APIC #0 from 0 to 2 on chip
Mar 12 15:00:30 mybox /kernel: Programming 24 pins in IOAPIC #0
Mar 12 15:00:30 mybox /kernel: FreeBSD/SMP: Multiprocessor motherboard: 2 CPUs
Mar 12 15:00:30 mybox /kernel: cpu0 (BSP): apic id: 0, version: 0x00050014, at
0xfee0
Mar 12 15:00:30 mybox /kernel: cpu1 (AP): apic id: 1, version: 0x00050014, at
0xfee0
...
Mar 12 15:00:30 mybox /kernel: SMP: AP CPU #1 Launched!
-- < Cut here > --
Excerpt from /var/log/messages - 5.2.1:
Mar 13 08:49:22 mybox kernel: CPU: Intel(R) Pentium(R) 4 CPU 2.60GHz (2593.68-MHz
686-class CPU)
Mar 13 08:49:22 mybox kernel: Origin = "GenuineIntel" Id = 0xf29 Stepping = 9
Mar 13 08:49:22 mybox kernel:
Features=0xbfebfbff
Mar 13 08:49:22 mybox kernel: Hyperthreading: 2 logical CPUs
Mar 13 08:49:22 mybox kernel: real memory = 394264576 (376 MB)
Mar 13 08:49:22 mybox kernel: avail memory = 376074240 (358 MB)
Mar 13 08:49:22 mybox kernel: MPTable:
Mar 13 08:49:22 mybox kernel: ioapic0: Changing APIC ID to 1
Mar 13 08:49:22 mybox kernel: ioapic0: Assuming intbase of 0
Mar 13 08:49:22 mybox kernel: ioapic0 irqs 0-23 on motherboard
Mar 13 08:49:22 mybox kernel: Pentium Pro MTRR support enabled
Mar 13 08:49:22 mybox kernel: cpu0 on motherboard
Mar 13 08:49:22 mybox kernel: npx0: [FAST]
___
[EMAIL PROTECTED] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Hyperthreading FreeBSD 4.9
I currently have FreeBSD 4.8 with hyperthreading enabled. I just cvsup to the latest version of FreeBSD to 4.9. When I do make buildkernel KERNCONF=FOO, I get an error of "unknown option "HTT"" Has hyperthreading been disabled in FreeBSD 4.9? Thanks JP _ Enjoy MSN 8 patented spam control and more with MSN 8 Dial-up Internet Service. Try it FREE for one month! http://join.msn.com/?page=dept/dialup ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Disabling Hyperthreading...
Deepak Naidu <[EMAIL PROTECTED]> writes: > I have installed FreeBSD 5.4 on Dell PowerEdge > 1750, which has Xeon processors. > > I have recompiled the kernel with SMP support(should I > add any option in Kernelconf file to disable it) > > When using top command I c 0123, processor it seems > hyper threading is enabled. > > How do I disable it, or is it diabled ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
enable smp / hyperthreading
Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 So I thought that it might help to but 'kern.smp.active=2' in /boot/loader.conf, but after a reboot it is back to 1 again. What am I missing here? regards, Jeppe Larsen ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading Issues
At 12:19 PM 5/19/2007 -0400, Dantavious wrote: Hi. It seems to me (From the limited knowledge that I have!) that my machine is not hyperthreading. I have done the following. maybe /etc/sysctl.conf: machdep.hyperthreading_allowed=1 ? -JD ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading Issues
On Saturday 19 May 2007 12:31:50 JD Bronson wrote: > machdep.hyperthreading_allowed=1 That did it thanks. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-11 19:52, "Timothy J. Luoma" <[EMAIL PROTECTED]> wrote: > > summary: should I disable hypertheading in the BIOS when running 5.3? > [...] > If YES, I wasn't clear if people meant "disable in BIOS" or just some > configuration setting in a *.conf file. FWIW, that should be enough, as far as FreeBSD is concerned. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Jan 11, 2005, at 6:52 PM, Timothy J. Luoma wrote: summary: should I disable hypertheading in the BIOS when running 5.3? Background info: I have a new Dell Dimension 3000 running 5.3. I noticed some huge pauses when copying a large # of files across the network. Googling around found some information about earlier versions of 5.x and Hyperthreading being detrimenatl for performance. Whether or not it was the source of the network copy problem, I am trying to decide if I should disable Hyperthreading. IMO there are times where 5.3 doesn't schedule the CPU as fairly as one would like. Times I've suspected this were during aggressive file activity on a few large files. I have HT disabled due to earlier problems with the combination of SATA and vinum resulting in a trashed fs with a late version of 5.2.1. The benefits of HT are too few for me to risk trashing the fs now its full. If you can reproduce your situation then I suggest disabling HT and see what happens. That's the only way anybody would know if HT is part of the problem or part of the solution. Iif YES, I wasn't clear if people meant "disable in BIOS" or just some configuration setting in a *.conf file. In the BIOS. (disabling HT will apparently mean I have to reinstall XP on the other drive. What does XP have to do with it? IIRC on Dell its F2 during the power-on diagnostics to reach the built-in BIOS config. That is where HT is to be disabled. Works exactly that way on my PowerEdge 400SC 2.8G P4. The only question is whether the key is F2 to get there or not. Was F2 this afternoon on my ancient Dell Optiplex 450 MHz P2 when I had to boot a DOS floppy to remap some bad blocks. -- David Kelly N4HHE, [EMAIL PROTECTED] Whom computers would destroy, they must first drive mad. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Timothy J. Luoma wrote: summary: should I disable hypertheading in the BIOS when running 5.3? It would certainly be worth trying this and seeing whether running as a purely single-proc system performs better for you. It's not exactly as if HyperThreading evolved out of a sensible plan like "let's design a multi-core CPU intended for parallel execution, or something like a m56k DSP with VLIW", the situation is more like "Intel created the P4 such a monsterously long pipeline that breaks x86 instructions into tiny u-ops which require a lot of functional units to be available, only the CPU still can't schedule things to use all of the available units much of the time, anyway, so hey, maybe we could run another processing thread on 'em and hope the additional work it can do outweighs the additional CPU resource contention and the additional overhead of doing SMP..." [ I have a non-HT P4 (a [EMAIL PROTECTED] Northwood) around, but I doubt I'd turn HT on with it even if it could. I'd rather use an AMD-64, or a G5, or even a recent P3 (Tualatin/Pentium-M) than another hyperthermal P4 spaceheater. ] Bah, I'm rambling, time to stop... :-) -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
David Kelly wrote: (disabling HT will apparently mean I have to reinstall XP on the other drive. What does XP have to do with it? IIRC on Dell its F2 during the power-on diagnostics to reach the built-in BIOS config. That is where HT is to be disabled. If you install and configure many flavors of Windows on a SMP system, that installation will not work if you move that image to a uni-proc system by swapping disks or otherwise removing CPU's (ie, by turning off HT'ing). I last saw this with a Win2K system, which immediately blue-screened with an "invalid SMP HAL" error very early in the boot. [ It doesn't surprise me that one would want or have to reinstall XP after disabling HyperThreading. There exist even less comprehensible reasons which oblige people to reinstall Windows ] -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Jan 11, 2005, at 9:18 PM, Chuck Swiger wrote: David Kelly wrote: (disabling HT will apparently mean I have to reinstall XP on the other drive. What does XP have to do with it? IIRC on Dell its F2 during the power-on diagnostics to reach the built-in BIOS config. That is where HT is to be disabled. If you install and configure many flavors of Windows on a SMP system, that installation will not work if you move that image to a uni-proc system by swapping disks or otherwise removing CPU's (ie, by turning off HT'ing). I last saw this with a Win2K system, which immediately blue-screened with an "invalid SMP HAL" error very early in the boot. OK, that makes Microsoft-logic sense. Had it in my head that he was saying the need to reinstall XP on a HD was to have a utility to toggle the HT bit in BIOS. OTOH I've heard of others toggling the HT bit but don't remember anything about having to reinstall XP. Last I had a similar dealing was with NT4SP4, possibly with the "upgrade" to NT4SP6 when I somehow lost one of my 450 MHz CPU's. Found instructions on how to revive the 2nd CPU but left it alone as it was far better for the company server to be running on one CPU than the risk of damaging the install worse than it already was. Last time I had to reinstall NT4SP6 it took 3 days of patch, reboot, repeat, before the OS install was complete. Decided it was time for a clean wipe installation on my laptop when Panther was released. Believe it took 15 minutes. About the same for a text-only installation of FreeBSD on my Dell Optiplex. -- David Kelly N4HHE, [EMAIL PROTECTED] Whom computers would destroy, they must first drive mad.
Re: Hyperthreading hurts 5.3?
On Jan 11, 2005, at 8:43 PM, Giorgos Keramidas wrote: On 2005-01-11 19:52, "Timothy J. Luoma" <[EMAIL PROTECTED]> wrote: summary: should I disable hypertheading in the BIOS when running 5.3? [...] If YES, I wasn't clear if people meant "disable in BIOS" or just some configuration setting in a *.conf file. FWIW, that should be enough, as far as FreeBSD is concerned. sorry to be dense, but which should be enough, BIOS or conf file? is the default to use or not use hyperthreading in the kernel/conf? ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Tue, 11 Jan 2005 23:52:11 -0500, Timothy Luoma <[EMAIL PROTECTED]> wrote: > > sorry to be dense, but which should be enough, BIOS or conf file? > > is the default to use or not use hyperthreading in the kernel/conf? By default the system will detect a HTT processor, but can only launch the second 'virtual' CPU core if you recompile the kernel with the SMP option enabled. I'm personally unclear why it'd be necessary to disable HTT in the BIOS if you're using a non-SMP kernel on a uniproc box. I'm experiencing some strangeness with a uniproc HTT-capable machine and SATA with either SMP or non-SMP kernels, so I'll try turning off HTT in the BIOS later this week and see if that helps. Bryan ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
> I'm personally unclear why it'd be necessary to disable HTT in the > BIOS if you're using a non-SMP kernel on a uniproc box. Maybe for the same reason you should better not use a non-SMP kernel if you have 2 CPU in your box. Try to keep hardware (BIOS) and OS consistent, even if they are supposed to know how to deal with inconsistencies. Olkivier ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Olivier Nicole writes: ON> Maybe for the same reason you should better not use a non-SMP kernel ON> if you have 2 CPU in your box. Is a hyperthreading CPU identical to a second CPU from the software's standpoint? If not, what are the differences? -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
> Is a hyperthreading CPU identical to a second CPU from the software's > standpoint? If not, what are the differences? I am not sure, but it is some how detected as 2 CPUs FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 cpu2 (AP): APIC ID: 6 cpu3 (AP): APIC ID: 7 Olivier ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Wed, Jan 12, 2005 at 12:02:37AM -0500, Bryan Fullerton wrote: > On Tue, 11 Jan 2005 23:52:11 -0500, Timothy Luoma <[EMAIL PROTECTED]> wrote: > > > > sorry to be dense, but which should be enough, BIOS or conf file? > > > > is the default to use or not use hyperthreading in the kernel/conf? > > By default the system will detect a HTT processor, but can only launch > the second 'virtual' CPU core if you recompile the kernel with the SMP > option enabled. Not true on 5.3+ GENERIC systems. If you look at dmesg, you'll see the second virtual CPU launched as well as the extra column in top(1) if you enable HTT in the BIOS. -- Jonathan Chen <[EMAIL PROTECTED]> -- Jesus saves. Allah forgives. Cthulu thinks you'd make a nice sandwich. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Jan 11, 2005, at 9:09 PM, David Kelly wrote: The benefits of HT are too few for me to risk trashing the fs now its full. That's a good enough reason for me. Iif YES, I wasn't clear if people meant "disable in BIOS" or just some configuration setting in a *.conf file. In the BIOS. Thanks... (disabling HT will apparently mean I have to reinstall XP on the other drive. What does XP have to do with it? Sorry to be unclear, XP is on the other drive. I called Creative Tech Support today to inquire why XP might die (BSOD) immediately on driver install for the serial port modem I bought from them. He immediately diagnosed this as a machine with HT enabled, and said that the way that IRQs are assigned is "different". (Someone else told me that Creative released new drivers but they hadn't helped.) He said the only way to use the modem would be to a) get a USB version [which I assumed wouldn't work well with FreeBSD] or b) disable HT, but because XP installs itself "differently" if it senses a "multiprocessor" I would have to reinstall. IIRC on Dell its F2 during the power-on diagnostics to reach the built-in BIOS config. That is where HT is to be disabled. Works exactly that way on my PowerEdge 400SC 2.8G P4. The only question is whether the key is F2 to get there or not. Was F2 this afternoon on my ancient Dell Optiplex 450 MHz P2 when I had to boot a DOS floppy to remap some bad blocks. Yup, mine is the same way. Shows "Setup F2" in initial flash screen (and F12 for 'boot menu' which, among other things, will let you manually boot from a 2nd hard drive, which is nice in case the OS on your 1st hard drive overwrites the MBR on reinstall (*cough like Windows cough*). [just arrived] On Jan 11, 2005, at 10:18 PM, Chuck Swiger wrote: [ It doesn't surprise me that one would want or have to reinstall XP after disabling HyperThreading. There exist even less comprehensible reasons which oblige people to reinstall Windows ] Well I may reinstall Windows for other reasons, including setting up a FAT32 partition that I can access r/w from FreeBSD and to fix the modem problem... not to mention the fact that Dell installs all this crap by default such as McAfee Virus Scanner (which is basically just an attempt to get people to buy it when it "expires"). Reinstalling Windows is so common I can now pretty much time the few steps I have to go interactive with it without it a) sitting idle or b) taking me away from getting real work done. TjL ps - thanks to all who responded. I'm going to disable HT, boot to FreeBSD and try another large file transfer and see if I see the large delays. If no, I'll copy the files I need off the XP drive and reinstall XP. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Jonathan Chen writes: JC> Not true on 5.3+ GENERIC systems. If you look at dmesg, you'll see the JC> second virtual CPU launched as well as the extra column in top(1) if JC> you enable HTT in the BIOS. Well, now I'm confusing. I have an Asus P4P800-E Deluxe MB with an Intel P4 processor mounted on it, and dmesg looks like this: FreeBSD 5.3-RELEASE #1: Mon Dec 27 05:52:34 CET 2004 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/FREEBIE ACPI APIC Table: Timecounter "i8254" frequency 1193182 Hz quality 0 CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2998.57-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf34 Stepping = 4 Features=0xbfebfbff Hyperthreading: 2 logical CPUs real memory = 1073414144 (1023 MB) avail memory = 1045057536 (996 MB) ioapic0: Changing APIC ID to 2 ioapic0 irqs 0-23 on motherboard npx0: [FAST] npx0: on motherboard npx0: INT 16 interface acpi0: on motherboard acpi0: Power Button (fixed) Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 acpi_timer0: <24-bit timer at 3.579545MHz> port 0x808-0x80b on acpi0 cpu0: on acpi0 pcib0: port 0xcf8-0xcff on acpi0 pci0: on pcib0 agp0: mem 0xf800-0xfbff at device 0.0 on pci0 pcib1: at device 1.0 on pci0 pcib1: could not get PCI interrupt routing table for \\_SB_.PCI0.P0P1 - AE_NOT_FOUND pci1: on pcib1 pci1: at device 0.0 (no driver attached) [...] Do I have two processors or not? The BIOS says that hyperthreading is enabled (and it wouldn't say anything at all if the processor were not HT-capable, according to the manual). Where's the second logical processor? I recompiled my own kernel but I didn't modify any of the CPU stuff (I don't think). -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-11 23:52, Timothy Luoma <[EMAIL PROTECTED]> wrote:
>On Jan 11, 2005, at 8:43 PM, Giorgos Keramidas wrote:
>>On 2005-01-11 19:52, "Timothy J. Luoma" <[EMAIL PROTECTED]> wrote:
>>>
>>> summary: should I disable hypertheading in the BIOS when running 5.3?
>>> [...]
>>> If YES, I wasn't clear if people meant "disable in BIOS" or just some
>>> configuration setting in a *.conf file.
>>
>> FWIW, that should be enough, as far as FreeBSD is concerned.
>
> sorry to be dense, but which should be enough, BIOS or conf file?
Oh, sorry about that. I must have beel sleepy when I replied and missed
that there were two questions there. I meant that disabling HT from the
BIOS setup should be enough for FreeBSD too.
> is the default to use or not use hyperthreading in the kernel/conf?
AFAICT from reading /usr/src/sys/i386/i386/mp_machdep.c, hyper-threading
support is always enabled in FreeBSD if it is also enabled in the BIOS.
The mp_topology() function contains, among other stuff:
222 void
223 mp_topology(void)
224 {
225 struct cpu_group *group;
226 int logical_cpus;
227 int apic_id;
228 int groups;
229 int cpu;
230
231 /* Build the smp_topology map. */
232 /* Nothing to do if there is no HTT support. */
233 if ((cpu_feature & CPUID_HTT) == 0)
234 return;
235 logical_cpus = (cpu_procinfo & CPUID_HTT_CORES) >> 16;
236 if (logical_cpus <= 1)
237 return;
___
freebsd-questions@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Wed, 12 Jan 2005 06:21:18 +0100 Anthony Atkielski <[EMAIL PROTECTED]> wrote: >Olivier Nicole writes: > >ON> Maybe for the same reason you should better not use a non-SMP kernel >ON> if you have 2 CPU in your box. > >Is a hyperthreading CPU identical to a second CPU from the software's >standpoint? If not, what are the differences? > Well, no, not exactly. The dual-cored CPUs share certain resources on the chip that are not shared in a multi-CPU situation, and that sharing means certain operations have to be handled differently. An MP setup has separate cache and TLB managment in each CPU, whereas P4 w/HT logical processors share this memory management circuitry. Alteration of a cache line requires notification of the other processor(s) in an MP situation to mark any corresponding line in its(their) cache(s) because multiple separate caches are involved, but notification is not necessary in the P4 w/HT situation because it's the same cache being seen by both logical processors. Alteration/invalidation of TLB entries requires notification to invalidate in an MP, so that the other CPU(s) can purge any corresponding TLB entries it(they) may have, but notification is not required in the P4 w/HT situation because both logical processors are refering to the same TLB. Again, unnecessary purging would be a performance hit. There must be some special handling of TLB entries in the P4 w/HT that I haven't seen documented. (There almost certainly is documentation; I just haven't seen it yet.) There must be some way to distinguish between TLB entries filled per orders of one logical processor from those filled per orders of the other logical processor. If there weren't, then one logical processor would use TLB entries for the address space running on the other logical processor, which would, of course, be Very Bad. But, to improve performance, there should be some way to share TLBs for the case of two threads running concurrently in the same address space. If anyone reading this knows the details of how this is handled in these chips, please post them here. Scott Bennett, Comm. ASMELG, CFIAG ** * Internet: bennett at cs.niu.edu * ** * "A well regulated and disciplined militia, is at all times a good * * objection to the introduction of that bane of all free governments * * -- a standing army." * *-- Gov. John Hancock, New York Journal, 28 January 1790 * ** ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-12 07:20, Anthony Atkielski <[EMAIL PROTECTED]> wrote: > Jonathan Chen writes: > JC> Not true on 5.3+ GENERIC systems. If you look at dmesg, you'll see the > JC> second virtual CPU launched as well as the extra column in top(1) if > JC> you enable HTT in the BIOS. > > Well, now I'm confusing. I have an Asus P4P800-E Deluxe MB with an > Intel P4 processor mounted on it, and dmesg looks like this: > > FreeBSD 5.3-RELEASE #1: Mon Dec 27 05:52:34 CET 2004 > [EMAIL PROTECTED]:/usr/obj/usr/src/sys/FREEBIE > ACPI APIC Table: > Timecounter "i8254" frequency 1193182 Hz quality 0 > CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2998.57-MHz 686-class CPU) > Origin = "GenuineIntel" Id = 0xf34 Stepping = 4 > > Features=0xbfebfbff > Hyperthreading: 2 logical CPUs > real memory = 1073414144 (1023 MB) > avail memory = 1045057536 (996 MB) > ioapic0: Changing APIC ID to 2 > ioapic0 irqs 0-23 on motherboard > npx0: [FAST] > npx0: on motherboard > npx0: INT 16 interface > acpi0: on motherboard > acpi0: Power Button (fixed) > Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 > acpi_timer0: <24-bit timer at 3.579545MHz> port 0x808-0x80b on acpi0 > cpu0: on acpi0 > pcib0: port 0xcf8-0xcff on acpi0 > pci0: on pcib0 > agp0: mem 0xf800-0xfbff at device > 0.0 on pci0 > pcib1: at device 1.0 on pci0 > pcib1: could not get PCI interrupt routing table for \\_SB_.PCI0.P0P1 - > AE_NOT_FOUND > pci1: on pcib1 > pci1: at device 0.0 (no driver attached) > [...] > > Do I have two processors or not? The BIOS says that hyperthreading is > enabled (and it wouldn't say anything at all if the processor were not > HT-capable, according to the manual). > > Where's the second logical processor? I recompiled my own kernel but I > didn't modify any of the CPU stuff (I don't think). You need to enable SMP too, to allow the FreeBSD kernel to use the second (hyper-threaded) CPU. My workstation is a P4 @ 2800, which does support HTT, but I haven't enabled SMP in my kernel configuration, so it is not used: % # grep 'options[[:space:]]*SMP' /usr/src/sys/conf/NOTES % options SMP # Symmetric MultiProcessor Kernel % # grep 'options[[:space:]]*SMP' \ % /usr/src/sys/`uname -m`/conf/`uname -v | sed -e 's:.*/::' ` % # dmesg % Copyright (c) 1992-2005 The FreeBSD Project. % Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994 % The Regents of the University of California. All rights reserved. % FreeBSD 6.0-CURRENT #0: Tue Jan 11 17:03:06 EET 2005 % [EMAIL PROTECTED]:/usr/obj/usr/src/sys/ORION % WARNING: WITNESS option enabled, expect reduced performance. % Timecounter "i8254" frequency 1193182 Hz quality 0 % CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2806.37-MHz 686-class CPU) % Origin = "GenuineIntel" Id = 0xf33 Stepping = 3 % Features=0xbfebfbff % Hyperthreading: 2 logical CPUs % real memory = 468647936 (446 MB) % avail memory = 449392640 (428 MB) % npx0: [FAST] % npx0: on motherboard % npx0: INT 16 interface % acpi0: on motherboard % acpi0: Power Button (fixed) % Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 % acpi_timer0: <32-bit timer at 3.579545MHz> port 0x4008-0x400b on acpi0 % cpu0: on acpi0 % acpi_button0: on acpi0 ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-11 22:18, Chuck Swiger <[EMAIL PROTECTED]> wrote: >David Kelly wrote: >>> (disabling HT will apparently mean I have to reinstall XP on the >>> other drive. >> >> What does XP have to do with it? IIRC on Dell its F2 during the >> power-on diagnostics to reach the built-in BIOS config. That is where >> HT is to be disabled. > > If you install and configure many flavors of Windows on a SMP system, > that installation will not work if you move that image to a uni-proc > system by swapping disks or otherwise removing CPU's (ie, by turning > off HT'ing). I last saw this with a Win2K system, which immediately > blue-screened with an "invalid SMP HAL" error very early in the boot. Moving a disk with Windows installed on it to another system has other problems too, although they are not (in general) as serious. Since the user doesn't have the source, many options are 'tuned by the installation process' to the system Windows is installed on. So it doesn't sound as surprising that it would require a reinstall when HTT is toggled :-) > [ It doesn't surprise me that one would want or have to reinstall XP after > disabling HyperThreading. There exist even less comprehensible reasons > which oblige people to reinstall Windows ] True. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Giorgos Keramidas writes:
GK> You need to enable SMP too, to allow the FreeBSD kernel to use the
GK> second (hyper-threaded) CPU.
I found it, in a file called SMP. Why is the SMP option tucked away in
a separate file?
I stuck this into the config and rebuilt the kernel. Seems to run fine.
I see that top has a C column now, and running a program in a continuous
loop takes up exactly 50% of the machine (and two such programs take up
exactly 100%), according to top.
Boot messages looked a bit different:
The Regents of the University of California. All rights reserved.
FreeBSD 5.3-RELEASE #0: Wed Jan 12 17:55:18 CET 2005
[EMAIL PROTECTED]:/usr/obj/usr/src/sys/FREEBIE-SMP
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2998.57-MHz 686-class CPU)
Origin = "GenuineIntel" Id = 0xf34 Stepping = 4
Features=0xbfebfbff
Hyperthreading: 2 logical CPUs
real memory = 1073414144 (1023 MB)
avail memory = 1045061632 (996 MB)
ACPI APIC Table:
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
cpu0 (BSP): APIC ID: 0
cpu1 (AP): APIC ID: 1
[...]
cpu0: on acpi0
cpu1: on acpi0
[...]
SMP: AP CPU #1 Launched!
So I guess it's all working now. That was easy.
I imagine this will give me a bit more horsepower for the buck,
although--with only 0.2% of the machine busy under normal load even with
a single processor--I guess I wasn't exactly processor-bound to begin
with (I'd run out of I/O capacity long before running out of processor).
But why not profit from what's there, eh?
--
Anthony
___
Re: Hyperthreading hurts 5.3?
Scott Bennett writes: SB> Well, no, not exactly. The dual-cored CPUs share certain resources SB> on the chip that are not shared in a multi-CPU situation, and that sharing SB> means certain operations have to be handled differently. An MP setup has SB> separate cache and TLB managment in each CPU ... What's TLB? SB> ... whereas P4 w/HT logical processors share this memory management SB> circuitry. Alteration of a cache line requires notification of the SB> other processor(s) in an MP situation to mark any corresponding line SB> in its(their) cache(s) because multiple separate caches are SB> involved, but notification is not necessary in the P4 w/HT situation SB> because it's the same cache being seen by both logical processors. SB> Alteration/invalidation of TLB entries requires notification to SB> invalidate in an MP, so that the other CPU(s) can purge any corresponding TLB SB> entries it(they) may have, but notification is not required in the P4 w/HT SB> situation because both logical processors are refering to the same TLB. Again, SB> unnecessary purging would be a performance hit. SB> There must be some special handling of TLB entries in the P4 w/HT that SB> I haven't seen documented. (There almost certainly is documentation; I just SB> haven't seen it yet.) There must be some way to distinguish between TLB SB> entries filled per orders of one logical processor from those filled per SB> orders of the other logical processor. If there weren't, then one logical SB> processor would use TLB entries for the address space running on the other SB> logical processor, which would, of course, be Very Bad. But, to improve SB> performance, there should be some way to share TLBs for the case of two SB> threads running concurrently in the same address space. If anyone reading SB> this knows the details of how this is handled in these chips, please post them SB> here. From what you say and from what I've read today, it sounds like hyperthreading comes close to providing two separate processors for heterogenous system loads (where each hyperthread is using slightly different processor resources at any given instant), but it may not buy much of anything for massively parallel compute-bound work, since both threads may want nearly the same things at the same time and will thus effectively be forced to spend a lot of time waiting for each other. Fortunately, my server has a very mixed load, as one would expect for a generic domain server, so hopefully it will profit from hyperthreading. And hopefully no weird stuff will happen because I've turned on HT (although offhand I'm not sure what would happen, unless there are hidden hardware conflicts or something specific and software-visible about HT in normal operation that might expose a bug). I'm not sure that I see how HT could affect Serial ATA disks, for example, any more than having two separate physical processors would. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-12 18:41, Anthony Atkielski <[EMAIL PROTECTED]> wrote: > Giorgos Keramidas writes: > > GK> You need to enable SMP too, to allow the FreeBSD kernel to use the > GK> second (hyper-threaded) CPU. > > I found it, in a file called SMP. Why is the SMP option tucked away in > a separate file? [...] The 'separate file' is NOTES. This file is actually the complete reference of options that the kernel supports, so it's not like the SMP option is hidden or something. > I imagine this will give me a bit more horsepower for the buck, > although--with only 0.2% of the machine busy under normal load even with > a single processor--I guess I wasn't exactly processor-bound to begin > with (I'd run out of I/O capacity long before running out of processor). > But why not profit from what's there, eh? Because it's not always a 'profit'. The locking and synchronization overhead is not always negligible. Please, read the rest of the thread too :-) - Giorgos ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Giorgos Keramidas writes: GK> The 'separate file' is NOTES. This file is actually the complete GK> reference of options that the kernel supports, so it's not like the SMP GK> option is hidden or something. I must have a magic special version of FreeBSD: # cd /usr/src/sys/i386/conf # grep SMP * NOTES:# SMP OPTIONS: NOTES:# The apic device can be used in both UP and SMP kernels, but is required NOTES:# for SMP kernels. Thus, the apic device is not strictly an SMP option, NOTES:# but it is a prerequisite for SMP. NOTES:# Be sure to disable 'cpu I386_CPU' for SMP kernels. NOTES:# Enabling this with an SMP kernel will cause the kernel to be unusable. NOTES:options I4B_SMP_WORKAROUND SMP:# SMP -- Generic kernel configuration file for FreeBSD/i386 SMP SMP:# $FreeBSD: src/sys/i386/conf/SMP,v 1.5.4.1 2004/10/23 20:04:00 kensmith Exp $ SMP:options SMP # The "options SMP" appears only in a file called SMP on my system. GK> Because it's not always a 'profit'. GK> GK> The locking and synchronization overhead is not always negligible. My experience with multiprocessing on other systems is that this overhead is rarely an issue. For single-threaded compute-bound user processes and occasionally for some similarly-designed OS processes it sometimes makes a difference; usually there's a net gain, though. At some specific number of processors (often 5 or more, but it depends on many things), the additional overhead associated with managing yet another processor (including hardware and software contention) causes global performance to diminish rather than increase. But I'd be very surprised to see that on any OS or platform with only two processors. There are also some key advantages to having more than one processor, such as the fact that the system is much more likely to remain responsive if a (typical single-threaded) process gets stuck in a loop. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Wed, 12 Jan 2005 18:29:01 +1300, Jonathan Chen <[EMAIL PROTECTED]> wrote: > On Wed, Jan 12, 2005 at 12:02:37AM -0500, Bryan Fullerton wrote: > > By default the system will detect a HTT processor, but can only launch > > the second 'virtual' CPU core if you recompile the kernel with the SMP > > option enabled. > > Not true on 5.3+ GENERIC systems. If you look at dmesg, you'll see the > second virtual CPU launched as well as the extra column in top(1) if > you enable HTT in the BIOS. You are incorrect. There is no SMP option in the 5.3-R i386 GENERIC config file as distributed. Other platforms (sparc64 and alpha) do ship with SMP enabled by default. They're not using HTT, though, so are irrelevant to this discussion. Bryan ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Wed, 12 Jan 2005 00:02:37 -0500, Bryan Fullerton <[EMAIL PROTECTED]> wrote: > I'm experiencing some strangeness with a uniproc HTT-capable machine > and SATA with either SMP or non-SMP kernels, so I'll try turning off > HTT in the BIOS later this week and see if that helps. Well, this is interesting. I disabled HTT in the BIOS and rebooted with a SMP kernel. As expected, there is only one CPU available after boot. However, FreeBSD still detects that the CPU is HTT-capable and prints the following in dmesg output: CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2793.01-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf33 Stepping = 3 Features=0xbfebfbff Hyperthreading: 2 logical CPUs If my sig11 issue doesn't recur now that HTT is off I'll go back to a non-SMP kernel and confirm there are no issues there too. Bryan ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On 2005-01-12 19:23, Anthony Atkielski <[EMAIL PROTECTED]> wrote: > Giorgos Keramidas writes: > > GK> The 'separate file' is NOTES. This file is actually the complete > GK> reference of options that the kernel supports, so it's not like the SMP > GK> option is hidden or something. > > I must have a magic special version of FreeBSD: > > # cd /usr/src/sys/i386/conf > # grep SMP * > NOTES:# SMP OPTIONS: Look in /usr/src/sys/conf/NOTES too. The machine independent kernel options are listed there, instead of the machine-dependent NOTES file. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Anthony Atkielski wrote: From what you say and from what I've read today, it sounds like hyperthreading comes close to providing two separate processors for heterogenous system loads (where each hyperthread is using slightly different processor resources at any given instant), but it may not buy much of anything for massively parallel compute-bound work, FWIW I tried numerical computations on a P4 with HT enabled: I expected using 2 threads might give *at least slightly* better results, but I could come to the conclusion that with 1, 2 or 4 threads the performance gain (or loss) was exactly zero. (BTW, an old AMD 2000 XP+ would in any case almost outperform a P4 3GHz, but that's another story). Obviously your use (as a server) is very different, and probably the one test I have done can't expect to achieve 100% coverage even in this field... but, anyway, just my 2 cents... bye av. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Wed, 12 Jan 2005 18:45:56 +0100 Anthony Atkielski <[EMAIL PROTECTED]> wrote: >Scott Bennett writes: > >SB> Well, no, not exactly. The dual-cored CPUs share certain resources >SB> on the chip that are not shared in a multi-CPU situation, and that sharing >SB> means certain operations have to be handled differently. An MP setup has >SB> separate cache and TLB managment in each CPU ... > >What's TLB? Translation Lookaside Buffer. (I know. It's a weird name. I think its origin was at IBM, which would explain the weirdness completely.) Its a collection of registers that contains the results of the most recent address translations. These results are kept around in order to avoid going through the full address translation process for addresses in pages for which address translation has already occurred. It's a big time-saver. When a virtual address is encountered that isn't in the TLB, then address translation proceeds from scratch, and the result replaces the least recently used entry in the TLB. > >SB> ... whereas P4 w/HT logical processors share this memory management >SB> circuitry. Alteration of a cache line requires notification of the >SB> other processor(s) in an MP situation to mark any corresponding line >SB> in its(their) cache(s) because multiple separate caches are >SB> involved, but notification is not necessary in the P4 w/HT situation >SB> because it's the same cache being seen by both logical processors. >SB> Alteration/invalidation of TLB entries requires notification to >SB> invalidate in an MP, so that the other CPU(s) can purge any corresponding >TLB >SB> entries it(they) may have, but notification is not required in the P4 w/HT >SB> situation because both logical processors are refering to the same TLB. >Again, >SB> unnecessary purging would be a performance hit. >SB> There must be some special handling of TLB entries in the P4 w/HT that >SB> I haven't seen documented. (There almost certainly is documentation; I >just >SB> haven't seen it yet.) There must be some way to distinguish between TLB >SB> entries filled per orders of one logical processor from those filled per >SB> orders of the other logical processor. If there weren't, then one logical >SB> processor would use TLB entries for the address space running on the other >SB> logical processor, which would, of course, be Very Bad. But, to improve >SB> performance, there should be some way to share TLBs for the case of two >SB> threads running concurrently in the same address space. If anyone reading >SB> this knows the details of how this is handled in these chips, please post >them >SB> here. > >>From what you say and from what I've read today, it sounds like >hyperthreading comes close to providing two separate processors for >heterogenous system loads (where each hyperthread is using slightly >different processor resources at any given instant), but it may not buy >much of anything for massively parallel compute-bound work, since both >threads may want nearly the same things at the same time and will thus >effectively be forced to spend a lot of time waiting for each other. I think that's probably close to the truth. For logic and number crunching, the two logical processors can proceed in parallel. But they will compete for any non-register memory access, for address translation time, and possibly other resources. I notice that the 5.2.1 boot messages refer to the second core as an AP, which I'm guessing stands for "attached processor". If that guess is correct, then it means that only the first core is able to perform certain functions, and the AP core has to get the first core to do those things for it when it needs them done. Typically, such restricted functions include things like starting I/O operations, handling I/O interrupts, setting the system clock, etc. Whether these restrictions are the actual ones, if there are any at all, in this situation, I do not know. > >Fortunately, my server has a very mixed load, as one would expect for a >generic domain server, so hopefully it will profit from hyperthreading. > What Intel claims is essentially that the HT-enabled CPUs allow snappier responses in interactive processes when a CPU-bound process is running. >And hopefully no weird stuff will happen because I've turned on HT >(although offhand I'm not sure what would happen, unless there are >hidden hardware conflicts or something specific and software-visible >about HT in normal operation that might expose a bug). I'm not sure >that I see how HT could affect Serial ATA disks, for example, any more >than having two separate physical processors wo
Re: Hyperthreading hurts 5.3?
Andrea Venturoli writes: AV> FWIW I tried numerical computations on a P4 with HT enabled: I expected AV> using 2 threads might give *at least slightly* better results, but I AV> could come to the conclusion that with 1, 2 or 4 threads the performance AV> gain (or loss) was exactly zero. Where these computations in which all threads were doing pretty much the same thing? And was it floating-point? (Doesn't the processor have just one FPU, or something like that?) AV> BTW, an old AMD 2000 XP+ would in any case almost outperform a P4 3GHz, AV> but that's another story. An AMD processor will also melt or catch fire if the CPU fan fails, whereas an Intel processor won't. I found this out the hard way, and so henceforth I'll be installing Intel processors. The cost savings one gets from buying AMD isn't enough to pay for a new motherboard or PC. AV> Obviously your use (as a server) is very different, and probably the AV> one test I have done can't expect to achieve 100% coverage even in AV> this field... but, anyway, just my 2 cents... I have no easy way to measure the performance on my system, so I'm mostly just speculating--but it seems logical. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Jan 12, 2005, at 12:34 AM, Timothy Luoma wrote: ps - thanks to all who responded. I'm going to disable HT, boot to FreeBSD and try another large file transfer and see if I see the large delays. If no, I'll copy the files I need off the XP drive and reinstall XP. Ok, well I disabled HT and still saw the delays. Then I figured out that it wasn't FreeBSD, it was Apple's ftpd. I started ftpd on the FreeBSD machine and used 'put' instead of 'get' and that worked just fine. Still, given all that's been said, I disabled HT and reinstalled XP. Thanks to all who shared their insight. TjL ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Scott Bennett writes: SB> I notice that the 5.2.1 boot messages refer to the second core as an SB> AP, which I'm guessing stands for "attached processor". If that SB> guess is correct, then it means that only the first core is able to SB> perform certain functions, and the AP core has to get the first core SB> to do those things for it when it needs them done. AP just stands for "application processor," from what I've seen. My impression from snooping in the code and looking elsewhere is that an AP is just a processor that is halted during system boot. The processor that executes the boot sequence is the bootstrap processor (BSP). Once the boot proceeds far enough to allow synchronization of multiple processors, the other processors (APs all) are started by the BSP. This doesn't necessarily mean that the BSP is special in any other way outside of startup or shutdown, and hopefully it is not, as that would defeat much of the conceptual purpose behind SMP. I know that on operating systems that insist on keeping one processor special for certain tasks, the speed of this processor often becomes a bottleneck on heavily loaded systems, as it tops out trying to handle all the "restricted" stuff for the other processors and itself. SB> What Intel claims is essentially that the HT-enabled CPUs allow SB> snappier responses in interactive processes when a CPU-bound process SB> is running. That I can believe. One of the great advantages to a multiple-processor system is that it's much less likely to bog down if a process decides to hog a processor (unless the process runs multiple threads). I think MP is more interesting for its ability to run completely independent processes or threads than it is for its ability to run multiple threads doing the same thing. Few applications require multiple high-speed processors churning through code all at once. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
> An AMD processor will also melt or catch fire if the CPU fan fails, > whereas an Intel processor won't. I found this out the hard way, and so Not always true, I had a P4 1.5 die on me for lack of fan. Now what was tha company selling a new box with no fan on the CPU is another story... Olivier ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Olivier Nicole writes: ON> Not always true, I had a P4 1.5 die on me for lack of fan. I understood that all recent Intel processors will first slow the clock and then halt completely if the die temperature rises too much, but there may be exceptions (or perhaps some processors run so hot that they will overheat without a fan even in the stopped state). Did it start up when you replaced the fan, or was it gone for good? In the case of my AMD processor, it reached a temperature of at least 110° C and still ran, but shortly thereafter a problem with memory management developed and worsened rapidly until the processor was completely dead. ON> Now what was tha company selling a new box with no fan on the CPU is ON> another story... I thought all the boxed P4 processors came with their own fan, so there should never be a case in which a PC is sold with a P4 but no CPU fan. In any case, now that I've decided to build my own servers from now on, there should be far fewer unpleasant surprises. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
RE: Hyperthreading hurts 5.3?
> -Original Message- > From: [EMAIL PROTECTED] [mailto:owner-freebsd- > [EMAIL PROTECTED] On Behalf Of Anthony Atkielski > Sent: Thursday, January 13, 2005 6:14 > To: freebsd-questions@freebsd.org > Subject: Re: Hyperthreading hurts 5.3? > > Andrea Venturoli writes: > > Where these computations in which all threads were doing pretty much the > same thing? And was it floating-point? (Doesn't the processor have > just one FPU, or something like that?) Yes Dual cored CPUs have a single FPU. > > An AMD processor will also melt or catch fire if the CPU fan fails, > whereas an Intel processor won't. I found this out the hard way, and so > henceforth I'll be installing Intel processors. The cost savings one > gets from buying AMD isn't enough to pay for a new motherboard or PC. This *used* to be true. I am using a AMD64 3000+ and the idle temperature is 28C. The room temp is around 12-14C. After asking this kid to crunch FPs for over 16 hrs, the processor temperature rose to only 38C. I am not using any special cooling gears, just the stock heatsink fan combo that came with the box pack. Indian Institute of Information Technology Subhro Sankha Kar Block AQ-13/1, Sector V Salt Lake City PIN 700091 India smime.p7s Description: S/MIME cryptographic signature
Re: Hyperthreading hurts 5.3?
Subhro writes: S> This *used* to be true. I am using a AMD64 3000+ and the idle S> temperature is 28C. The room temp is around 12-14C. After asking this S> kid to crunch FPs for over 16 hrs, the processor temperature rose to S> only 38C. I am not using any special cooling gears, just the stock S> heatsink fan combo that came with the box pack. The case temperature on my FreeBSD server runs at about 36° C with a room temperature of 25° C, and the 3.0 GHz Intel P4 processor is at about 44° and very nearly idle (0.5% busy). After running the processor at 100% for a few minutes, it gets up to 51° (I haven't tried the experiment beyond that, and the system is never 100% under normal conditions). There are seven fans (I'm not taking any chances): two that blow into the case over the disk drives, one that blows down onto the motherboard (directly over the CPU), and three that blow through and out of the power supply--plus the P4 CPU fan. They draw air through filters so they don't create that much movement, but I like the redundancy. My desktop running WinXP has an AMD Athlon 1800-something. The processor runs at about 59° and the case is at 29°; this case has only three fans, one in the PS, on inward fan on the case, and a tiny CPU fan over the processor. The arrangement of the MB is such that the CPU doesn't have a very clear airflow over it. The CPU fan has been replaced twice, as the first fans were sleeve bearings that failed almost immediately (I installed my own ball-bearing fan after that). The case fan was my own addition. On one occasion the CPU froze after the fan failed, but it did not seem to break. I don't know if this model of processor includes any protections. It would be nice if someone would design processors that did not require active cooling, as the need for a CPU fan to keep the system from self-destructing is a major weak point for the hardware. Thank goodness modern operating systems idle the processor when it's not in use. I shudder to think what it would be like under old versions of Windows (including Win9x) that just looped when idle. FreeBSD runs cool as a cucumber, even though it handles all my Web and mail and DNS and NTP traffic. Which reminds me: I'm still looking for a way to monitor system temperature at securelevel=3 on my FreeBSD system, so suggestions are welcome. Healthd is fine but it won't work at securelevel=3. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
off-topic, but... On Thu, Jan 13, 2005 at 01:43:54AM +0100, Anthony Atkielski wrote: > AV> BTW, an old AMD 2000 XP+ would in any case almost outperform a P4 3GHz, > AV> but that's another story. > > An AMD processor will also melt or catch fire if the CPU fan fails, > whereas an Intel processor won't. I found this out the hard way, and so > henceforth I'll be installing Intel processors. The cost savings one > gets from buying AMD isn't enough to pay for a new motherboard or PC. This also depends on your motherboard having overheat protection (ie shuts itself down when the CPU temperature goes too high). My ASUS A7N8X calls this feature 'C.O.P.' -- CPU overheating protection. Choose your motherboard wisely and you'll avoid this problem. --Stijn -- It's harder to read code than to write it. -- Joel Spolsky, http://www.joelonsoftware.com/articles/fog69.html pgpSvKCBPHFu7.pgp Description: PGP signature
Re: Hyperthreading hurts 5.3?
On Thu, 13 Jan 2005 02:11:27 +0100 Anthony Atkielski <[EMAIL PROTECTED]> wrote: >Scott Bennett writes: > >SB> I notice that the 5.2.1 boot messages refer to the second core as an >SB> AP, which I'm guessing stands for "attached processor". If that >SB> guess is correct, then it means that only the first core is able to >SB> perform certain functions, and the AP core has to get the first core >SB> to do those things for it when it needs them done. > >AP just stands for "application processor," from what I've seen. My >impression from snooping in the code and looking elsewhere is that an AP >is just a processor that is halted during system boot. The processor >that executes the boot sequence is the bootstrap processor (BSP). Once >the boot proceeds far enough to allow synchronization of multiple >processors, the other processors (APs all) are started by the BSP. Oh, good. That sounds much better than what I was thinking. > >This doesn't necessarily mean that the BSP is special in any other way >outside of startup or shutdown, and hopefully it is not, as that would >defeat much of the conceptual purpose behind SMP. I know that on >operating systems that insist on keeping one processor special for >certain tasks, the speed of this processor often becomes a bottleneck on >heavily loaded systems, as it tops out trying to handle all the >"restricted" stuff for the other processors and itself. Usually that sort of restriction has a basis in hardware. For example, IBM's MP mainframes *used to* require that the same processor that started an I/O operation be the one that fielded the interrupt(s) upon completion of the operation. Some machines also had the main processor/attached processor configuration, in which the attached processor had no access to the I/O hardware at all, so all I/O handling had to be done by the main processor because the AP had no way to do it. > >SB> What Intel claims is essentially that the HT-enabled CPUs allow >SB> snappier responses in interactive processes when a CPU-bound process >SB> is running. > >That I can believe. One of the great advantages to a multiple-processor >system is that it's much less likely to bog down if a process decides to >hog a processor (unless the process runs multiple threads). I think MP >is more interesting for its ability to run completely independent >processes or threads than it is for its ability to run multiple >threads doing the same thing. Few applications require multiple >high-speed processors churning through code all at once. > My main interest in such things at present is for dividing the workload in fluid dynamics and, most especially, geophysical fluid dynamics models. Those, of course, do immense amounts of number-crunching with occasional, massive bouts of I/O. I want to play around with making a two-threaded version of a GFD model (either atmospheric or oceanic) to see what, if any, savings there may be in elapsed time by running on both cores vs. just one. Such a model would have both threads doing essentially the same things, though operating upon different parts of the arrays involved. But first, I still have to get a usable FreeBSD system going. :-( Scott Bennett, Comm. ASMELG, CFIAG ** * Internet: bennett at cs.niu.edu * ** * "A well regulated and disciplined militia, is at all times a good * * objection to the introduction of that bane of all free governments * * -- a standing army." * *-- Gov. John Hancock, New York Journal, 28 January 1790 * ** ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Anthony Atkielski wrote: Where these computations in which all threads were doing pretty much the same thing? Not exactly the same algorithm and on different set of data. And was it floating-point? Yes. (Doesn't the processor have just one FPU, or something like that?) I don't really know (I made this test almost for fun and curiosity), but I really supposed this must be true. Anyway I saw both CPU at 100%. An AMD processor will also melt or catch fire if the CPU fan fails, whereas an Intel processor won't. In the past. Nowadays they have some sort of protection. BTW I've already seen a couple of (old) Athlons with a failing fan; they run overheated probably for months with occasional system lockups, but they are now working good with a new fan. I'll stop here, we are going OT (and flaming :)... bye av. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
> Did it start up when you replaced the fan, or was it gone for good? It was dead for good, well it is still dead as a matter of fact :) > I thought all the boxed P4 processors came with their own fan, so there > should never be a case in which a PC is sold with a P4 but no CPU fan. So did I, so did I, but one sees strange things when buying a machine from a cheap assembly shop (I was not the first buyer, I just got the machine when it became unusable and then I was curious so I opened it, what the first owner never did). Olivier ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Andrea Venturoli writes: AV> Not exactly the same algorithm and on different set of data. But similar machine instructions, perhaps? AV> Yes. Just the contention for the FPU alone might have had the effect of single-threading the workload. That plus the SMP overhead might give you a zero or negative gain with HT. AV> In the past. AV> Nowadays they have some sort of protection. Unfortunately, AMD lost my business when the first processor nearly burst into flames. I try not to make the same mistake twice. And I've seen examples of AMD processors that _have_ burst into flames, so why take a chance? For me the weakest parts of any machine are the fans and the disk drives, because they have to move. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Olivier Nicole writes: ON> It was dead for good, well it is still dead as a matter of fact :) The AMD processor on my XP system overheated and stalled a few times, before I realized that the (brand-new) fan had failed. It still runs okay now, though, with a reliable fan. The other AMD processor, on my server, dramatically overheated for 8-12 hours at a time (process stuck in a loop--I never found out why). It damaged something that failed intermittently at first (segment violations in the kernel and in daemons that should never have such problems), then got worse and worse over a few days, until it failed completely. ON> So did I, so did I, but one sees strange things when buying a machine ON> from a cheap assembly shop (I was not the first buyer, I just got the ON> machine when it became unusable and then I was curious so I opened it, ON> what the first owner never did). I decided to build my own. I was tired of not knowing what was inside the machine, and finding out the hard and expensive way that many corners had been cut. I also got tired of having stacks and stacks of unused stereo mini-speakers, ultra-cheap keyboards, and equally cheap mice. Not to mention paying for Windows and a boatload of absolutely useless garbage software that I was just going to wipe away immediately in favor of FreeBSD (and I configure my FreeBSD systems to run FreeBSD exclusively--none of this dual-boot stuff). It gives me strange pleasure to think that the current server has never gotten anywhere near Windows. FreeBSD was the first OS to deflower the virgin disk drives. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Anthony Atkielski wrote: Andrea Venturoli writes: AV> Not exactly the same algorithm and on different set of data. But similar machine instructions, perhaps? Yes, both numerical computations. Basically one thread would model geometry and the other would mesh it. Frequent stall would arise, as the two process would only by chance require the same time, even so the two CPUs were always at full load (!?!?!?). I also tried different combinations, e.g. three modelling threads and one mesher with, again, equal timings. BTW, it's worth to mention, I *have* to use a compiler that knows nothing about SSE or the like, so all is done with FPU instructions as in the old 387s... Just the contention for the FPU alone might have had the effect of single-threading the workload. I've come to the same conclusion. Still I can't put this together with 100% load on both processors. If, as someone said, there is only one FPU, *how* are these figures coming out??? I would have expected something like 50%-50% (instead of 100%-0% of the single threaded version). *If* there is only one FPU, I'd expect both virtual processors being frequently idle waiting for each other. That plus the SMP overhead might give you a zero or negative gain with HT. I tried a multithreaded version on a UP machine (nonsense, I know): the locking overhead is there, but very minimal: a process which takes 16 minutes will require, maybe, 3 seconds more. bye av. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
Andrea Venturoli writes: AV> I've come to the same conclusion. Still I can't put this together with AV> 100% load on both processors. If, as someone said, there is only one AV> FPU, *how* are these figures coming out??? The operating system tracks a dispatch of a processor into a process thread. After that, it has no idea whether the processor is actually doing anything or not--from the OS' standpoint, the processor is "running." So if one thread in one logical processor is actually executing instructions, and the other is stalled while waiting for a shared resource in the processor, the OS will still consider both threads to be "running" and will charge all of the elapsed time as processor time ... giving you a figure of 100% busy. AV> I would have expected something like 50%-50% (instead of 100%-0% of AV> the single threaded version). *If* there is only one FPU, I'd expect AV> both virtual processors being frequently idle waiting for each AV> other. Yes ... but the OS can't see that, and so OS monitoring tools can't report it. -- Anthony ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
> The other AMD processor, on my server, dramatically overheated for 8-12 > hours at a time (process stuck in a loop--I never found out why). It > damaged something that failed intermittently at first (segment > violations in the kernel and in daemons that should never have such > problems), then got worse and worse over a few days, until it failed > completely. It was not my machine, maybe it had been giving some warnings, but the one in charge failed to notice them. > I decided to build my own. I was tired of not knowing what was inside > the machine, and finding out the hard and expensive way that many > corners had been cut. I also got tired of having stacks and stacks of I rely on a shop that I trust, and for servers, I give the exact requirements :) And of course I always open a new box before I power it on... > unused stereo mini-speakers, ultra-cheap keyboards, and equally cheap > mice. Not to mention paying for Windows and a boatload of absolutely At least we do not pay for Windows, that is Thailand :) (partial BS as we have a site licence for Windows, shame!) Olivier ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading hurts 5.3?
On Thu, 13 Jan 2005 21:38:08 +0100 Andrea Venturoli <[EMAIL PROTECTED]> wrote: >Anthony Atkielski wrote: >> Andrea Venturoli writes: >> >> AV> Not exactly the same algorithm and on different set of data. >> >> But similar machine instructions, perhaps? > >Yes, both numerical computations. >Basically one thread would model geometry and the other would mesh it. >Frequent stall would arise, as the two process would only by chance >require the same time, even so the two CPUs were always at full load >(!?!?!?). I also tried different combinations, e.g. three modelling Makes sense. >threads and one mesher with, again, equal timings. > >BTW, it's worth to mention, I *have* to use a compiler that knows >nothing about SSE or the like, so all is done with FPU instructions as >in the old 387s... > That may make each thread take longer than if it could use the SSE instructions, but is unrelated to your other issue. > >> Just the contention for the FPU alone might have had the effect of >> single-threading the workload. > >I've come to the same conclusion. Still I can't put this together with >100% load on both processors. If, as someone said, there is only one >FPU, *how* are these figures coming out??? I would have expected >something like 50%-50% (instead of 100%-0% of the single threaded >version). *If* there is only one FPU, I'd expect both virtual processors >being frequently idle waiting for each other. > They most likely are. You seem to be forgetting that the "idling" in question is handled within the CPU, not by the kernel. In other words, it happens effectively *during* an instruction on the "idled" core, not by kernel processing between thread switches, so the instruction just takes longer than it otherwise would, sort of like waiting for a memory access to complete. No interrupt occurs. The core just sits and twiddles its electrons until the resource it's queued upon becomes available to it, and then it proceeds to complete the "idled" instruction. > >> That plus the SMP overhead might give >> you a zero or negative gain with HT. > >I tried a multithreaded version on a UP machine (nonsense, I know): the >locking overhead is there, but very minimal: a process which takes 16 >minutes will require, maybe, 3 seconds more. > Was that using MPI? Or some other thread management package? Scott Bennett, Comm. ASMELG, CFIAG 836 Greenbrier Road, Apt. 4 DeKalb, Illinois 60115 ** * Internet: bennett at cs.niu.edu * ** * "A well regulated and disciplined militia, is at all times a good * * objection to the introduction of that bane of all free governments * * -- a standing army." * *-- Gov. John Hancock, New York Journal, 28 January 1790 * ** ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: SMP vs. Hyperthreading?
On Sat, Mar 13, 2004 at 02:37:37PM +0100, [EMAIL PROTECTED] wrote:
> Hi,
>
> I've got a machine with a P4 that supports HTT (Hyperthreading) so I
> thought about setting up a SMP-kernel.
>
> Under 4.9 it seems to work (see excerpts from /var/log/messages
> below), whereas on the same exact hardware under 5.2.1 I don't see two
> virtual CPUs working.
>
> For a first check I've run "cpuburn" (i.e. burnP6). Under 4.9 with one
> "cpuburn" process active "top" etc. show a cpu-load of about 50% which
> for me means SMP/HTT is active.
>
> Under 5.2.1 it's a different story though: /var/log/messages shows
> that there are 2 CPUs but the message indicating the second CPU has
> been launched is missing ("/kernel: SMP: AP CPU #1 Launched!"). When I
> run a "cpuburn"-Test under 5.2.1 CPU load indicated by "top" shows
> 100% so I assume SMP/HTT is not active.
>
>
> So my primary question is - how do I get SMP running under 5.2.1 with
> a hyperthreading-capable P4??
I installed 5.2 and that came ready to run afther the install. I didn't
have to do anything for it.
--
Alex
Articles based on solutions that I use:
http://www.kruijff.org/alex/index.php?dir=docs/FreeBSD/
___
[EMAIL PROTECTED] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
RE: SMP vs. Hyperthreading?
> Hi,
>
> I've got a machine with a P4 that supports HTT (Hyperthreading) so I
> thought about setting up a SMP-kernel.
SMP <> HT. I'm not an expert on this, but when I went to an Intel conference
a couple years ago which discussed hyperthreading, it was made pretty clear
it wasn't the same as SMP. But, like I said, I'm not an expert so I don't
know what exactly its doing at the very low levels.
> Under 5.2.1 it's a different story though: /var/log/messages shows
> that there are 2 CPUs but the message indicating the second CPU has
> been launched is missing ("/kernel: SMP: AP CPU #1 Launched!"). When I
> run a "cpuburn"-Test under 5.2.1 CPU load indicated by "top" shows
> 100% so I assume SMP/HTT is not active.
That is the message for the second CPU. The first is CPU #0 and is always
active. Every dual-cpu machine I've installed SMP kernel on only shows the
second CPU launching.
> So my primary question is - how do I get SMP running under 5.2.1 with
> a hyperthreading-capable P4??
I haven't used 5.x, but in 4.9, there is a specific line in the kernel
config for hyperthreading support (to which I've read mixed reviews on this
list).
Good luck
Brent
___
[EMAIL PROTECTED] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Hyperthreading FreeBSD 4.9
On Wed, Oct 29, 2003 at 01:51:32PM -0800, John Palmer wrote: > I currently have FreeBSD 4.8 with hyperthreading enabled. I just cvsup to > the latest version of FreeBSD to 4.9. When I do make buildkernel > KERNCONF=FOO, I get an error of "unknown option "HTT"" Has hyperthreading > been disabled in FreeBSD 4.9? It's controlled by sysctl, as long as you have a SMP kernel. Kris pgp0.pgp Description: PGP signature
Re: Hyperthreading FreeBSD 4.9
--On Wednesday, October 29, 2003 13:51:32 -0800 John Palmer <[EMAIL PROTECTED]> wrote: I currently have FreeBSD 4.8 with hyperthreading enabled. I just cvsup to the latest version of FreeBSD to 4.9. When I do make buildkernel KERNCONF=FOO, I get an error of "unknown option "HTT"" Has hyperthreading been disabled in FreeBSD 4.9? Read /usr/src/UPDATING. Thanks JP _ Enjoy MSN 8 patented spam control and more with MSN 8 Dial-up Internet Service. Try it FREE for one month! http://join.msn.com/?page=dept/dialup ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]" -- Larry Rosenman http://www.lerctr.org/~ler Phone: +1 972-414-9812 E-Mail: [EMAIL PROTECTED] US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749 pgp0.pgp Description: PGP signature
Re: Hyperthreading FreeBSD 4.9
On Wed, Oct 29, 2003 at 01:51:32PM -0800, John Palmer wrote: > I currently have FreeBSD 4.8 with hyperthreading enabled. I just cvsup to > the latest version of FreeBSD to 4.9. When I do make buildkernel > KERNCONF=FOO, I get an error of "unknown option "HTT"" Has hyperthreading > been disabled in FreeBSD 4.9? The answer to your question is cunningly hidden at the top of the /usr/src/UPDATING file -- you know, the one the instructions are always telling you to read -- and it's hidden there because it's a secret, and that's the one place no-one would ever look for it. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way PGP: http://www.infracaninophile.co.uk/pgpkey Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK pgp0.pgp Description: PGP signature
Re: Hyperthreading FreeBSD 4.9
Thanks From: Larry Rosenman <[EMAIL PROTECTED]> To: John Palmer <[EMAIL PROTECTED]>, [EMAIL PROTECTED] Subject: Re: Hyperthreading FreeBSD 4.9 Date: Wed, 29 Oct 2003 15:59:08 -0600 --On Wednesday, October 29, 2003 13:51:32 -0800 John Palmer <[EMAIL PROTECTED]> wrote: I currently have FreeBSD 4.8 with hyperthreading enabled. I just cvsup to the latest version of FreeBSD to 4.9. When I do make buildkernel KERNCONF=FOO, I get an error of "unknown option "HTT"" Has hyperthreading been disabled in FreeBSD 4.9? Read /usr/src/UPDATING. Thanks JP _ Enjoy MSN 8 patented spam control and more with MSN 8 Dial-up Internet Service. Try it FREE for one month! http://join.msn.com/?page=dept/dialup ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]" -- Larry Rosenman http://www.lerctr.org/~ler Phone: +1 972-414-9812 E-Mail: [EMAIL PROTECTED] US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749 << attach3 >> _ Send instant messages to anyone on your contact list with MSN Messenger 6.0. Try it now FREE! http://msnmessenger-download.com ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Missing machdep.hlt_logical_cpus on hyperthreading..
Hi! I'm having a problem, sysctl can't find machdep.hlt_logical_cpus. My machine is a dual xeon with hyperthreading enabled, running 4.9. I also would like to know what that "Warning: Pentium 4 CPU: PSE disabled" means. See below: sysctl: unknown oid 'machdep.hlt_logical_cpus' FreeBSD guldivar.globalwire.se 4.9-RELEASE FreeBSD 4.9-RELEASE #1: Mon Nov 24 14:59:32 CET 2003 [EMAIL PROTECTED]:/usr/src/sys/compile/FLASHZGI i386 Copyright (c) 1992-2003 The FreeBSD Project. Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994 The Regents of the University of California. All rights reserved. FreeBSD 4.9-RELEASE #1: Mon Nov 24 14:59:32 CET 2003 [EMAIL PROTECTED]:/usr/src/sys/compile/FLASHZGI Timecounter "i8254" frequency 1193182 Hz CPU: Intel(R) XEON(TM) CPU 1.80GHz (1799.80-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf24 Stepping = 4 Features=0x3febfbff Hyperthreading: 2 logical CPUs real memory = 1073676288 (1048512K bytes) config> di sn0 No such device: sn0 Invalid command or syntax. Type `?' for help. config> di lnc0 No such device: lnc0 Invalid command or syntax. Type `?' for help. config> di ie0 No such device: ie0 Invalid command or syntax. Type `?' for help. config> di fe0 No such device: fe0 Invalid command or syntax. Type `?' for help. config> di cs0 No such device: cs0 Invalid command or syntax. Type `?' for help. config> di bt0 No such device: bt0 Invalid command or syntax. Type `?' for help. config> di adv0 No such device: adv0 Invalid command or syntax. Type `?' for help. config> q avail memory = 1041534976 (1017124K bytes) Programming 24 pins in IOAPIC #0 IOAPIC #0 intpin 2 -> irq 0 Programming 24 pins in IOAPIC #1 Programming 24 pins in IOAPIC #2 FreeBSD/SMP: Multiprocessor motherboard: 4 CPUs cpu0 (BSP): apic id: 0, version: 0x00050014, at 0xfee0 cpu1 (AP): apic id: 1, version: 0x00050014, at 0xfee0 cpu2 (AP): apic id: 6, version: 0x00050014, at 0xfee0 cpu3 (AP): apic id: 7, version: 0x00050014, at 0xfee0 io0 (APIC): apic id: 8, version: 0x00178020, at 0xfec0 io1 (APIC): apic id: 9, version: 0x00178020, at 0xfec8 io2 (APIC): apic id: 10, version: 0x00178020, at 0xfec80400 Preloaded elf kernel "kernel" at 0xc0414000. Preloaded userconfig_script "/boot/kernel.conf" at 0xc041409c. Warning: Pentium 4 CPU: PSE disabled Pentium Pro MTRR support enabled md0: Malloc disk Using $PIR table, 14 entries at 0xc00f3f20 npx0: on motherboard npx0: INT 16 interface pcib0: on motherboard IOAPIC #0 intpin 16 -> irq 2 IOAPIC #0 intpin 18 -> irq 9 IOAPIC #0 intpin 17 -> irq 10 pci0: on pcib0 pcib1: at device 2.0 on pci0 pci2: on pcib1 pci2: (vendor=0x8086, dev=0x1461) at 28.0 pcib2: at device 29.0 on pci2 IOAPIC #2 intpin 0 -> irq 11 pci4: on pcib2 pci4: (vendor=0x8086, dev=0x1008) at 1.0 irq 11 pcib3: at device 3.0 on pci4 pci5: on pcib3 asr0: mem 0xf800-0xfbff irq 11 at device 3.1 on pci4 asr0: major=154 asr0: ADAPTEC 3410S FW Rev. 370F, 4 channel, 256 CCBs, Protocol I2O pci2: (vendor=0x8086, dev=0x1461) at 30.0 pcib4: at device 31.0 on pci2 pci3: on pcib4 pci0: at 29.0 irq 2 pcib5: at device 30.0 on pci0 pci1: on pcib5 pci1: at 2.0 irq 9 fxp0: port 0xc880-0xc8bf mem 0xfe6a-0xfe6bfff f,0xfe6fe000-0xfe6fefff irq 10 at device 3.0 on pci1 fxp0: Ethernet address 00:e0:81:20:f7:7c inphy0: on miibus0 inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto isab0: at device 31.0 on pci0 isa0: on isab0 atapci0: port 0xffa0-0xffaf,0-0x3,0-0x7,0-0x3,0-0 x7 irq 9 at device 31.1 on pci0 ata0: at 0x1f0 irq 14 on atapci0 ata1: at 0x170 irq 15 on atapci0 pci0: (vendor=0x8086, dev=0x2483) at 31.3 irq 10 orm0: at iomem 0xc-0xc7fff,0xc8000-0xc97ff,0xc9800-0xcf7ff,0xc f800-0xd0fff on isa0 pmtimer0 on isa0 fdc0: at port 0x3f0-0x3f5,0x3f7 irq 6 drq 2 on isa0 atkbdc0: at port 0x60,0x64 on isa0 atkbd0: flags 0x1 irq 1 on atkbdc0 kbd0 at atkbd0 vga0: at port 0x3c0-0x3df iomem 0xa-0xb on isa0 sc0: at flags 0x100 on isa0 sc0: VGA <16 virtual consoles, flags=0x300> sio0: configured irq 4 not in bitmap of probed irqs 0 sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0 sio0: type 8250 sio1: configured irq 3 not in bitmap of probed irqs 0 ppc0: parallel port not found. APIC_IO: Testing 8254 interrupt delivery APIC_IO: routing 8254 via IOAPIC #0 intpin 2 IP packet filtering initialized, divert disabled, rule-based forwarding enabled, default to accept, unlimited logging SMP: AP CPU #3 Launched! SMP: AP CPU #1 Launched! SMP: AP CPU #2 Launched! acd0: CDROM at ata0-master PIO4 Mounting root from ufs:/dev/da0s1a da0 at asr0 bus 0 target 1 lun 0 da0: Fixed Direct Access SCSI-2 device da0: Tagged Queueing Enabled da0: 70004MB (143368192 512 byte sectors: 255H 63S/T 8924C) ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Missing machdep.hlt_logical_cpus on hyperthreading..
Hi, i'm reposting this since I didn't get any answer at all... I'm having a problem, sysctl can't find machdep.hlt_logical_cpus. My machine is a dual xeon with hyperthreading enabled, running 4.9. I also would like to know what that "Warning: Pentium 4 CPU: PSE disabled" means. See below: sysctl: unknown oid 'machdep.hlt_logical_cpus' FreeBSD guldivar.globalwire.se 4.9-RELEASE FreeBSD 4.9-RELEASE #1: Mon Nov 24 14:59:32 CET 2003 [EMAIL PROTECTED]:/usr/src/sys/compile/FLASHZGI i386 Copyright (c) 1992-2003 The FreeBSD Project. Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994 The Regents of the University of California. All rights reserved. FreeBSD 4.9-RELEASE #1: Mon Nov 24 14:59:32 CET 2003 [EMAIL PROTECTED]:/usr/src/sys/compile/FLASHZGI Timecounter "i8254" frequency 1193182 Hz CPU: Intel(R) XEON(TM) CPU 1.80GHz (1799.80-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf24 Stepping = 4 Features=0x3febfbff Hyperthreading: 2 logical CPUs real memory = 1073676288 (1048512K bytes) config> di sn0 No such device: sn0 Invalid command or syntax. Type `?' for help. config> di lnc0 No such device: lnc0 Invalid command or syntax. Type `?' for help. config> di ie0 No such device: ie0 Invalid command or syntax. Type `?' for help. config> di fe0 No such device: fe0 Invalid command or syntax. Type `?' for help. config> di cs0 No such device: cs0 Invalid command or syntax. Type `?' for help. config> di bt0 No such device: bt0 Invalid command or syntax. Type `?' for help. config> di adv0 No such device: adv0 Invalid command or syntax. Type `?' for help. config> q avail memory = 1041534976 (1017124K bytes) Programming 24 pins in IOAPIC #0 IOAPIC #0 intpin 2 -> irq 0 Programming 24 pins in IOAPIC #1 Programming 24 pins in IOAPIC #2 FreeBSD/SMP: Multiprocessor motherboard: 4 CPUs cpu0 (BSP): apic id: 0, version: 0x00050014, at 0xfee0 cpu1 (AP): apic id: 1, version: 0x00050014, at 0xfee0 cpu2 (AP): apic id: 6, version: 0x00050014, at 0xfee0 cpu3 (AP): apic id: 7, version: 0x00050014, at 0xfee0 io0 (APIC): apic id: 8, version: 0x00178020, at 0xfec0 io1 (APIC): apic id: 9, version: 0x00178020, at 0xfec8 io2 (APIC): apic id: 10, version: 0x00178020, at 0xfec80400 Preloaded elf kernel "kernel" at 0xc0414000. Preloaded userconfig_script "/boot/kernel.conf" at 0xc041409c. Warning: Pentium 4 CPU: PSE disabled Pentium Pro MTRR support enabled md0: Malloc disk Using $PIR table, 14 entries at 0xc00f3f20 npx0: on motherboard npx0: INT 16 interface pcib0: on motherboard IOAPIC #0 intpin 16 -> irq 2 IOAPIC #0 intpin 18 -> irq 9 IOAPIC #0 intpin 17 -> irq 10 pci0: on pcib0 pcib1: at device 2.0 on pci0 pci2: on pcib1 pci2: (vendor=0x8086, dev=0x1461) at 28.0 pcib2: at device 29.0 on pci2 IOAPIC #2 intpin 0 -> irq 11 pci4: on pcib2 pci4: (vendor=0x8086, dev=0x1008) at 1.0 irq 11 pcib3: at device 3.0 on pci4 pci5: on pcib3 asr0: mem 0xf800-0xfbff irq 11 at device 3.1 on pci4 asr0: major=154 asr0: ADAPTEC 3410S FW Rev. 370F, 4 channel, 256 CCBs, Protocol I2O pci2: (vendor=0x8086, dev=0x1461) at 30.0 pcib4: at device 31.0 on pci2 pci3: on pcib4 pci0: at 29.0 irq 2 pcib5: at device 30.0 on pci0 pci1: on pcib5 pci1: at 2.0 irq 9 fxp0: port 0xc880-0xc8bf mem 0xfe6a-0xfe6bfff f,0xfe6fe000-0xfe6fefff irq 10 at device 3.0 on pci1 fxp0: Ethernet address 00:e0:81:20:f7:7c inphy0: on miibus0 inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto isab0: at device 31.0 on pci0 isa0: on isab0 atapci0: port 0xffa0-0xffaf,0-0x3,0-0x7,0-0x3,0-0 x7 irq 9 at device 31.1 on pci0 ata0: at 0x1f0 irq 14 on atapci0 ata1: at 0x170 irq 15 on atapci0 pci0: (vendor=0x8086, dev=0x2483) at 31.3 irq 10 orm0: at iomem 0xc-0xc7fff,0xc8000-0xc97ff,0xc9800-0xcf7ff,0xc f800-0xd0fff on isa0 pmtimer0 on isa0 fdc0: at port 0x3f0-0x3f5,0x3f7 irq 6 drq 2 on isa0 atkbdc0: at port 0x60,0x64 on isa0 atkbd0: flags 0x1 irq 1 on atkbdc0 kbd0 at atkbd0 vga0: at port 0x3c0-0x3df iomem 0xa-0xb on isa0 sc0: at flags 0x100 on isa0 sc0: VGA <16 virtual consoles, flags=0x300> sio0: configured irq 4 not in bitmap of probed irqs 0 sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0 sio0: type 8250 sio1: configured irq 3 not in bitmap of probed irqs 0 ppc0: parallel port not found. APIC_IO: Testing 8254 interrupt delivery APIC_IO: routing 8254 via IOAPIC #0 intpin 2 IP packet filtering initialized, divert disabled, rule-based forwarding enabled, default to accept, unlimited logging SMP: AP CPU #3 Launched! SMP: AP CPU #1 Launched! SMP: AP CPU #2 Launched! acd0: CDROM at ata0-master PIO4 Mounting root from ufs:/dev/da0s1a da0 at asr0 bus 0 target 1 lun 0 da0: Fixed Direct Access SCSI-2 device da0: Tagged Queueing Enabled da0: 70004MB (143368192 512 byte sectors: 255H 63S/T 8924C)
Re: enable smp / hyperthreading
On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: > Hi > > I've just installed 6.0-RELASE and am trying to get SMP to work (I have af > Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and > according to dmesg the two CPUs are found: > > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > cpu0 (BSP): APIC ID: 0 > cpu1 (AP): APIC ID: 1 > > But I'm not sure that both are enabled, because at this is at the end of > dmesg and I dont see the other CPU being enabled somewhere: > > SMP: AP CPU #1 Launched! I think it is referring to the Auxiliary Processor (AP), because the BSP (don't know what that stands for, though) is obviously already active. > According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP > doesnt seem to be disabled: > > kern.smp.cpus: 2 > kern.smp.disabled: 0 > kern.smp.active: 1 sysctl -d kern.smp.active kern.smp.active: Number of Auxillary Processors (APs) that were successfully started This is the number of _extra_ CPUs, which chould be 1. Roland -- R.F.Smith (http://www.xs4all.nl/~rsmith/) Please send e-mail as plain text. public key: http://www.xs4all.nl/~rsmith/pubkey.txt pgpnrnQu316T8.pgp Description: PGP signature
Re: enable smp / hyperthreading
On Mon, 7 Nov 2005 20:05:24 +0100 Roland Smith <[EMAIL PROTECTED]> wrote: > On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: > > Hi > > > > I've just installed 6.0-RELASE and am trying to get SMP to work (I > > have af Pentium 4 with HT). So I've compiled the kernel with > > 'options SMP' and according to dmesg the two CPUs are found: > > > > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > > cpu0 (BSP): APIC ID: 0 > > cpu1 (AP): APIC ID: 1 > > > > But I'm not sure that both are enabled, because at this is at the > > end of dmesg and I dont see the other CPU being enabled somewhere: > > > > SMP: AP CPU #1 Launched! > > I think it is referring to the Auxiliary Processor (AP), because the > BSP (don't know what that stands for, though) is obviously already > active. > > According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP > > doesnt seem to be disabled: > > > > kern.smp.cpus: 2 > > kern.smp.disabled: 0 > > kern.smp.active: 1 > > sysctl -d kern.smp.active > kern.smp.active: Number of Auxillary Processors (APs) that were > successfully started > > This is the number of _extra_ CPUs, which chould be 1. > > Roland If hyperthreading is working the ouput of 'top' should have a C column and will show either a 0 or a 1. AFAIK HTT is still disabled because of a security risk. See: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc If you do not believe you are at risk, there is a work around included in the above site. YMMV. I have been known to be wrong before. :-) Robert ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: enable smp / hyperthreading
On Mon, 7 Nov 2005 11:16:19 -1000 Robert Marella <[EMAIL PROTECTED]> wrote: > On Mon, 7 Nov 2005 20:05:24 +0100 > Roland Smith <[EMAIL PROTECTED]> wrote: > > > On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: > > > Hi > > > > > > I've just installed 6.0-RELASE and am trying to get SMP to work (I > > > have af Pentium 4 with HT). So I've compiled the kernel with > > > 'options SMP' and according to dmesg the two CPUs are found: > > > > > > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > > > cpu0 (BSP): APIC ID: 0 > > > cpu1 (AP): APIC ID: 1 > > > > > > But I'm not sure that both are enabled, because at this is at the > > > end of dmesg and I dont see the other CPU being enabled somewhere: > > > > > > SMP: AP CPU #1 Launched! > > > > I think it is referring to the Auxiliary Processor (AP), because the > > BSP (don't know what that stands for, though) is obviously already > > active. > > > According to 'sysctl -a' there are 2 CPUs, but only 1 active and > > > SMP doesnt seem to be disabled: > > > > > > kern.smp.cpus: 2 > > > kern.smp.disabled: 0 > > > kern.smp.active: 1 > > > > sysctl -d kern.smp.active > > kern.smp.active: Number of Auxillary Processors (APs) that were > > successfully started > > > > This is the number of _extra_ CPUs, which chould be 1. > > > > Roland > > If hyperthreading is working the ouput of 'top' should have a C column > and will show either a 0 or a 1. > > AFAIK HTT is still disabled because of a security risk. See: > > ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc > > If you do not believe you are at risk, there is a work around included > in the above site. > > YMMV. I have been known to be wrong before. :-) > > Robert > Replying to myself. It seems that once again I am wrong. I commented out the machdep.hyperthreading_allowed=1 in /boot/loader.conf on my 6.0 system and I still have the C column and showing 2 processors. Sorry about the noise. Robert ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: enable smp / hyperthreading
On Mon, 07 Nov 2005 11:16:19 -1000, Robert Marella wrote: > ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc > That did the trick, I think :) -- regards, Jeppe W. Larsen "Logic is the beginning of wisdom; not the end." ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: enable smp / hyperthreading
On Monday 07 November 2005 18:53, [EMAIL PROTECTED] wrote: > Hi > > I've just installed 6.0-RELASE and am trying to get SMP to work (I have af > Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and > according to dmesg the two CPUs are found: > > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > cpu0 (BSP): APIC ID: 0 > cpu1 (AP): APIC ID: 1 > > But I'm not sure that both are enabled, because at this is at the end of > dmesg and I dont see the other CPU being enabled somewhere: > > SMP: AP CPU #1 Launched! > > According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP > doesnt seem to be disabled: > > kern.smp.cpus: 2 > kern.smp.disabled: 0 > kern.smp.active: 1 > > So I thought that it might help to but 'kern.smp.active=2' in > /boot/loader.conf, but after a reboot it is back to 1 again. > > What am I missing here? I'm sure people more knowledgeable than me will be able to confirm or comment further on the following but here goes anyway. From my point of view, using SMP with a single HT processor is a waste of time unless you routinely run multiple programmes which require an approximately equal amount of CPU time or you need to keep about half of your CPU time free for other programs. For example, encoding video with mplayer on a P4 with SMP enabled only used one virtual CPU. It encodes approx. twice as fast with SMP switched off (and HT switched off in BIOS) There does appear to be some lost CPU cycles due to HT switching too. Note that I've not done any serious testing or looked deeply into this subject. This is simply my limited experience. -- Dave ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: enable smp / hyperthreading
On Thu, 17 Nov 2005 23:02:39 +, dgmm wrote: > From my point of view, using SMP with a single HT processor is a waste of > time > unless you routinely run multiple programmes which require an approximately > equal amount of CPU time or you need to keep about half of your CPU time free > for other programs. What about running 'make' with some -j options? Wouldnt that take advantage of the "two" CPUs better than if running without HT? And 'make' is used quite often ;) -- vh Jeppe W. Larsen "Logic is the beginning of wisdom; not the end." ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
SMP with hyperthreading CPU (5.3)?
Hi, I've got a 3GHz P4 system with hyperthreading enabled in the BIOS. For this system I've built a SMP-kernel (kernel config-file "SMP" that comes with 5.3). However SMP doesn't seem to be enabled - at least I don't seen the usual messages like "CPU ... launched" that's common with SMP configurations. The only thing I'm seeing are the following entries during boot: CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2992.71-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf34 Stepping = 4 Features=0xbfebfbff Hyperthreading: 2 logical CPUs Neither does "top" show anything about a second (logical) cpu being active, nor does ps. So do I have two logical CPUs active on this system? If not - what should I do besides enabling "SMP" in the kernel config file (sure enough "cpu I386_CPU" which effectively disables SMP is commented out) Thanks much in advance for any hints, -ewald ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: Missing machdep.hlt_logical_cpus on hyperthreading..
Stefan Cars wrote: Hi, i'm reposting this since I didn't get any answer at all... I'm having a problem, sysctl can't find machdep.hlt_logical_cpus. My machine is a dual xeon with hyperthreading enabled, running 4.9. I also would like to know what that "Warning: Pentium 4 CPU: PSE disabled" means. Stefan, In your kernel configuration file, you need following: optionsSMP# Symmetric MultiProcessor Kernel optionsAPIC_IO# Symmetric (APIC) I/O Then machdep.hlt_logical_cpus is in your sysctl. Can't help you with the "PSE disabled" thing. Cheers, Rob. ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
no hyperthreading in FreeBSD 9?
Hi, I just upgraded from 8-STABLE to 9-STABLE on my dual Xeon (nocona). Now I have in my boot messages: ... root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hlt_logical_cpus does not exist. root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hyperthreading_allowed does not exist. ... So isn't hyperthreading not available anymore in FreeBSD 9? Regards, Marco -- If you want me to be a good little bunny just dangle some carats in front of my nose. -- Lauren Bacall ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
FreeBSD and Intel Hyperthreading technology.
Hello, I have an Intel P4 2.8Ghz processor with Hyperthreading (HT). The dmesg displays a message saying HT is present and 2 logical CPUs present.I tried toggling the setting in BIOS but no difference. How does the FBSD(v5.4 stable) kernel deal with HT ? Do the internal workings( maybe locking, per processor data or other things) change as compared to a simple non-HT processor ? or does it use employ SMP methods to deal with the 2 logical CPUs presented by a HT processor ? I want to do kernel programming on FBSD and my project partners have non-HT CPUs.How much difference will HT make ? can it be avoided ? TIA. Regards, Pranav Peshwe --- One of the greatest victories you can gain over someone is to beat him at politeness. - Josh Billings ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
hyperthreading CPU and broken scheduling?
i have machune with intel's CPU with hyperthreading. it is detected right, but only first thread is ever used. top shows at least 50% idle no matter what i run! what's wrong? root@:/usr62/src/sys/amd64/compile/serwer.tensor.gdynia.pl Timecounter "i8254" frequency 1193182 Hz quality 0 CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (3000.13-MHz K8-class CPU) Origin = "GenuineIntel" Id = 0xf62 Stepping = 2 Features=0xbfebfbff Features2=0xe41d,> AMD Features=0x20100800 AMD Features2=0x1 Logical CPUs per core: 2 real memory = 1072562176 (1022 MB) avail memory = 1021456384 (974 MB) ACPI APIC Table: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 ioapic0 irqs 0-23 on motherboard acpi0: on motherboard acpi0: Power Button (fixed) Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 acpi_timer0: <24-bit timer at 3.579545MHz> port 0x1008-0x100b on acpi0 cpu0: on acpi0 acpi_throttle0: on cpu0 cpu1: on acpi0 acpi_throttle1: on cpu1 acpi_throttle1: failed to attach P_CNT device_attach: acpi_throttle1 attach returned 6 ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Status of hyperthreading in FreeBSD
"Netbooks" based on Intel's "Atom" microprocessor are turning into big hits this Christmas season. The Atom, a super-low-power x86 processor, is an "in-order" machine, which means that except for a few special cases it can spend a lot of time waiting for data to arrive when it encounters a cache miss. So, hyperthreading may make sense on this kind of processor as compared to one with out-of-order execution. Which raises a question: What's the status of FreeBSD's support for hyperthreading? As far as I know, after it was revealed that some processes on a machine with hyperthreading could "spy" on others, and also that hyperthreading didn't always improve performance on high end processors, the feature was turned off by default. But on single-user machines, or on servers where the CPU was likely to be shared by two processes that were both privileged anyway, it might make sense to re-enable it. But has this feature of the scheduler been maintained well enough for this to be a good idea? If not, would it worth looking into updating it so that FreeBSD runs well on the Atom? --Brett Glass ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: SMP with hyperthreading CPU (5.3)?
If not - what should I do besides enabling "SMP" in the kernel config file (sure enough "cpu I386_CPU" which effectively disables SMP is commented out) I haven't updated my system since August, but back then the "apic" device was also required. 5.3 may be different. This is the relevant section from my 5.2-CURRENT hyperthreading kernel from last August. # To make an SMP kernel, the next two are needed options SMP # Symmetric MultiProcessor Kernel device apic# I/O APIC ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: SMP with hyperthreading CPU (5.3)?
On Sat, Oct 30, 2004 at 01:43:09PM -0700, Luke wrote: > I haven't updated my system since August, but back then the "apic" device > was also required. 5.3 may be different. > This is the relevant section from my 5.2-CURRENT hyperthreading kernel > from last August. > > # To make an SMP kernel, the next two are needed > options SMP # Symmetric MultiProcessor Kernel > device apic# I/O APIC > Sorry, forgot to say, that I've got both of them in my kernel config file, i.e. "SMP" and "apic" - however I don't get the characteristic "CPU... launched" messages upon boot. This brings me to another point: What's the best way (besides checking /var/log/messages) to tell whether SMP is active? Does "top" display cpu load for hyperthreading (as opposed to multiprocessor) systems too? -ewald ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: SMP with hyperthreading CPU (5.3)?
[EMAIL PROTECTED]:/home/killer/] sysctl kern.smp.active kern.smp.active: 0 > On Sat, Oct 30, 2004 at 01:43:09PM -0700, Luke wrote: >> I haven't updated my system since August, but back then the "apic" >> device >> was also required. 5.3 may be different. >> This is the relevant section from my 5.2-CURRENT hyperthreading kernel >> from last August. >> >> # To make an SMP kernel, the next two are needed >> options SMP # Symmetric MultiProcessor Kernel >> device apic# I/O APIC >> > > Sorry, forgot to say, that I've got both of them in my kernel config > file, i.e. "SMP" and "apic" - however I don't get the characteristic > "CPU... launched" messages upon boot. > > This brings me to another point: What's the best way (besides checking > /var/log/messages) to tell whether SMP is active? > > Does "top" display cpu load for hyperthreading (as opposed to > multiprocessor) systems too? > > -ewald > > > ___ > [EMAIL PROTECTED] mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "[EMAIL PROTECTED]" > -- www.6s-gaming.com ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: no hyperthreading in FreeBSD 9?
On 13 Jan 2012, at 16:30, Marco Beishuizen wrote: > Hi, > > I just upgraded from 8-STABLE to 9-STABLE on my dual Xeon (nocona). Now I > have in my boot messages: > ... > root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hlt_logical_cpus does not > exist. > root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hyperthreading_allowed does > not exist. > ... > > So isn't hyperthreading not available anymore in FreeBSD 9? http://svnweb.freebsd.org/base/release/9.0.0/UPDATING?r1=222852&r2=222853&; Seems to imply HT is enabled by default and new sysctls are used to take logical CPUs offline. How many CPUs does your boot message suggest FreeBSD 9 is reporting? - Mark___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: no hyperthreading in FreeBSD 9?
> > > Hi, > > > > I just upgraded from 8-STABLE to 9-STABLE on my dual Xeon (nocona). Now I > > have in my boot messages: > > ... > > root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hlt_logical_cpus does not > > exist. > > root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hyperthreading_allowed does > > not exist. > > ... > > > > So isn't hyperthreading not available anymore in FreeBSD 9? I'm not sure what you mean by this double negative. If you mean "Is hyperthreading still available on FreeBSD?", the answer is yes. If you mean "Can hyperthreading still be disabled on FreeBSD?" the answer is still yes-- only some problematic and redundant means of disabling it that were present in earlier versions of FreeBSD have been removed. (The primary commit is: http://svnweb.freebsd.org/base?view=revision&revision=222853 .) You can still use machdep.hyperthreading_allowed, but it is now only a (loader) tunable, and not also a sysctl, so you can only set it at boot time (via loader.conf(5), or by using "set ..." on the loader(8) command line), and you cannot change it on the fly after the system is up and running. > > http://svnweb.freebsd.org/base/release/9.0.0/UPDATING?r1=222852&r2=222853&; > > Seems to imply HT is enabled by default and new sysctls are used to take > logical CPUs offline. > Yes -- although that has been the case for a while, and the OIDs are not all sysctls (some are (loader) tunables or device hints (cf. device.hints(5)), and they are not new. b. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: no hyperthreading in FreeBSD 9?
On Fri, 13 Jan 2012, the wise Mark Blackman wrote: On 13 Jan 2012, at 16:30, Marco Beishuizen wrote: Hi, I just upgraded from 8-STABLE to 9-STABLE on my dual Xeon (nocona). Now I have in my boot messages: ... root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hlt_logical_cpus does not exist. root: /etc/rc.d/sysctl: WARNING: sysctl machdep.hyperthreading_allowed does not exist. ... So isn't hyperthreading not available anymore in FreeBSD 9? http://svnweb.freebsd.org/base/release/9.0.0/UPDATING?r1=222852&r2=222853&; Seems to imply HT is enabled by default and new sysctls are used to take logical CPUs offline. How many CPUs does your boot message suggest FreeBSD 9 is reporting? Yeah, I just deleted the lines from sysctl.conf and it doesn't seem to make a difference at all (2 cpu's x 2 threads). Sorry, Marco -- Who on earth would eat a charred caterpillar!? No, no, you SINGE 'em! You SINGE 'em and eat 'em! ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Can I disable HyperThreading in OS?
Hi, I have a dual XEON smp box. There is option about disable HTT in bios, but it can't work. It's still display 4 cpu in my OS. Can I disablt HTT in OS directly? I am running FreeBSD 4.11. Regards. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: FreeBSD and Intel Hyperthreading technology.
On Oct 5, 2005, at 11:48 AM, Pranav Peshwe wrote: Hello, I have an Intel P4 2.8Ghz processor with Hyperthreading (HT). The dmesg displays a message saying HT is present and 2 logical CPUs present.I tried toggling the setting in BIOS but no difference. How does the FBSD(v5.4 stable) kernel deal with HT ? Do the internal workings( maybe locking, per processor data or other things) change as compared to a simple non-HT processor ? or does it use employ SMP methods to deal with the 2 logical CPUs presented by a HT processor ? I want to do kernel programming on FBSD and my project partners have non-HT CPUs.How much difference will HT make ? can it be avoided ? I would suspect that if you do not run an SMP kernel it won't matter Chad --- Chad Leigh -- Shire.Net LLC Your Web App and Email hosting provider [EMAIL PROTECTED] ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
Wojciech Puchar wrote: i have machune with intel's CPU with hyperthreading. it is detected right, but only first thread is ever used. top shows at least 50% idle no matter what i run! what's wrong? root@:/usr62/src/sys/amd64/compile/serwer.tensor.gdynia.pl Timecounter "i8254" frequency 1193182 Hz quality 0 CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (3000.13-MHz K8-class CPU) Origin = "GenuineIntel" Id = 0xf62 Stepping = 2 Features=0xbfebfbff DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE> Features2=0xe41d,> AMD Features=0x20100800 AMD Features2=0x1 Logical CPUs per core: 2 real memory = 1072562176 (1022 MB) avail memory = 1021456384 (974 MB) ACPI APIC Table: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 ioapic0 irqs 0-23 on motherboard acpi0: on motherboard acpi0: Power Button (fixed) Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000 acpi_timer0: <24-bit timer at 3.579545MHz> port 0x1008-0x100b on acpi0 cpu0: on acpi0 acpi_throttle0: on cpu0 cpu1: on acpi0 acpi_throttle1: on cpu1 acpi_throttle1: failed to attach P_CNT device_attach: acpi_throttle1 attach returned 6 ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]" To enable hyperthreading, try setting the following in /etc/sysctl.conf: machdep.hyperthreading_allowed=1 and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
Wojciech Puchar wrote: http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]" To enable hyperthreading, try setting the following in /etc/sysctl.conf: machdep.hyperthreading_allowed=1 and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). did /etc/rc.d/sysctl start and works. quite strange that FreeBSD disables hyperthreading at start. IIRC there has been some discussion about possible vulnerabilities when hyperthreading is enabled. If you google around you will find it. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]" To enable hyperthreading, try setting the following in /etc/sysctl.conf: machdep.hyperthreading_allowed=1 and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). did /etc/rc.d/sysctl start and works. quite strange that FreeBSD disables hyperthreading at start. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
On 2007-11-18 11:43, Wojciech Puchar <[EMAIL PROTECTED]> wrote: >>> http://lists.freebsd.org/mailman/listinfo/freebsd-questions >>> To unsubscribe, send any mail to >>> "[EMAIL PROTECTED]" >> To enable hyperthreading, try setting the following in /etc/sysctl.conf: >> >> machdep.hyperthreading_allowed=1 >> >> and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). > > did /etc/rc.d/sysctl start and works. Please, use loader.conf to change `machdep.hyperthreading_allowed'. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
On Sun, 18 Nov 2007 12:29:32 +0200, Manolis Kiagias wrote: > Wojciech Puchar wrote: > > i have machune with intel's CPU with hyperthreading. > > > > it is detected right, but only first thread is ever used. > > > > top shows at least 50% idle no matter what i run! > > > > what's wrong? > To enable hyperthreading, try setting the following in /etc/sysctl.conf: > > machdep.hyperthreading_allowed=1 > > and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). would an SMP kernel be required to properly use hyperthreading, or would just the above sysctl setting be enough ? -- Regards, /\_/\ "All dogs go to heaven." [EMAIL PROTECTED](0 0) http://www.openmalaysiablog.com/ +==oOO--(_)--OOo==+ | for a in past present future; do| | for b in clients employers associates relatives neighbours pets; do | | echo "The opinions here in no way reflect the opinions of my $a $b." | | done; done | +=+ ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
Re: hyperthreading CPU and broken scheduling?
In response to Dinesh Nair <[EMAIL PROTECTED]>: > On Sun, 18 Nov 2007 12:29:32 +0200, Manolis Kiagias wrote: > > > Wojciech Puchar wrote: > > > i have machune with intel's CPU with hyperthreading. > > > > > > it is detected right, but only first thread is ever used. > > > > > > top shows at least 50% idle no matter what i run! > > > > > > what's wrong? > > To enable hyperthreading, try setting the following in /etc/sysctl.conf: > > > > machdep.hyperthreading_allowed=1 > > > > and reboot (or execute sysctl machdep.hyperthreading_allowed=1 by hand). > > would an SMP kernel be required to properly use hyperthreading, or would > just the above sysctl setting be enough ? The SMP kernel is required as well. -- Bill Moran http://www.potentialtech.com ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
When is it worth enabling hyperthreading?
Hi, Could someone explain me in which cases it is useful to enable hyperthreading on a machine running FreeBSD 8.0 and in which other cases it is not a good idea? Is that possible that hyperthreading is disadvantageous unless the number of active (non-sleeping) threads is really high? For example, if I have an i7 CPU with 4 physical cores and that I run some multi-threaded code that has only 4 threads, it will run almost always (twice) slower with hyperthreading enabled than when I disable it in the BIOS. If I understand correctly, hyperthreading has the advantage of being able to do CPU context switching faster than the OS, but it does this context switching systematically instead of only when requested, so it slows things down unless the number of running (non-sleeping) threads is greater or equal to let say the number of physical threads x 1.5-1.75. Thanks! ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
When is it worth enabling hyperthreading?
On Wed, 07 Oct 2009 23:24:48 -0400 Pierre-Luc Drouin wrote: >Could someone explain me in which cases it is useful to enable >hyperthreading on a machine running FreeBSD 8.0 and in which other cases >it is not a good idea? Is that possible that hyperthreading is >disadvantageous unless the number of active (non-sleeping) threads is >really high? > >For example, if I have an i7 CPU with 4 physical cores and that I run >some multi-threaded code that has only 4 threads, it will run almost >always (twice) slower with hyperthreading enabled than when I disable it >in the BIOS. If I understand correctly, hyperthreading has the advantage >of being able to do CPU context switching faster than the OS, but it No. Both context execute simultaneously. Each logical CPU of the two logical CPUs in a core has its own set of registers, LDT and GDT pointer registers, and instruction counter. Both compete for the same remaining set of resources: DAT, TLB, FPU, cache (all levels for a given core), busses to off-chip resources, and--most critically--pipeline slots per clock cycle. Any time a resource shared by the two logical CPUs (what the logical CPUs execute are called "CPU threads" or "hyperthreads") is in use by one logical CPU, it is unavailable for use by the other logical CPU. If a logical CPU needs a resource unavailable due to its being in use by the other logical CPU, the late-comer's processing is suspended until the resource is released by the other logical CPU. Such a lockout situation is not directly detectable in software because the locked-out instruction is still in execution; it's just taking more than the usual number of cycles to complete. On a P4 Prescott chip or the late models of single-cored Xeons, the pipeline structure is apparently less than ideal for sustained simultaneous execution; i.e., there are frequent pairings of instructions that require more than the available pipeline slots of the types required by the two parallel instructions, which causes one of them to spin until the other moves on, opening the next cycle's set of pipeline slots. A simple case can demonstrate the problem, although on most systems this example would likely be infrequent. There is only one FPU pipeline on these chips, so two floating-point instructions executing simultaneously will result in one getting the FPU pipeline slot for the current cycle, while the other one spins until the next cycle, whereupon the other side will spin, etc. What is actually the more common occurrence is that other types of instruction pairs will require, for example, four slots of a type that only has three pipelines. The Core i7 chips (don't know about the other Core iN series) are alleged to have an improved assortment of pipelines w.r.t. typical instruction mixes, although I think there is still only one FPU per core, so the parallelism is supposed to be rather more effective on these chips than on their forerunners in the Pentium/Xeon series. It has been quite a while since I last tried measuring it, but IIRC, a "make buildworld" on my 3.4 GHz P4 Prescott takes about one to two minutes longer elapsed time in non-hyperthreading mode with MAKEFLAGS set to "-j3" than it does with hyperthreading enabled and MAKEFLAGS set to "-j5" (i.e., something like 52 - 53 minutes instead of 51 minutes and a few seconds). Your quad-core Core i7 chips ought to provide a much greater benefit with hyperthreading enabled, relatively speaking. The traditional recommendation for the -j flag for make(1) is 3*nCPUs, but hyperthreading doesn't give you a full CPU's worth of extra processing, so your quad-core chips won't give you a full 8 CPUs' worth. In other words, a single, large, parallel make job probably should have -j set to something under 24 yet still greater than 12, as a guess perhaps 20ish. :-) But do try it yourself at different -j values, and let us know how your timings turn out on that chip, along with the model number of the chip. >does this context switching systematically instead of only when >requested, so it slows things down unless the number of running >(non-sleeping) threads is greater or equal to let say the number of >physical threads x 1.5-1.75. > In general, there is a slight gain, although running parallel floating-point activities is a break-even situation and not worth the bother unless you're just trying to learn OpenMP or some such. When I've disabled hyperthreading, interactive response has often seemed a tad less snappy when running some CPU-bound process at the same time. OTOH, with hyperthreading enabled, I sometimes notice a bit more jerkiness in things like scrolling in firefox, but it's not easy to tell what's really happening there because firefox typically has at least 7 threads itself. :-) Like Bill Moran
Re: Status of hyperthreading in FreeBSD
Brett Glass wrote: "Netbooks" based on Intel's "Atom" microprocessor are turning into big hits this Christmas season. The Atom, a super-low-power x86 processor, is an "in-order" machine, which means that except for a few special cases it can spend a lot of time waiting for data to arrive when it encounters a cache miss. So, hyperthreading may make sense on this kind of processor as compared to one with out-of-order execution. Which raises a question: What's the status of FreeBSD's support for hyperthreading? As far as I know, after it was revealed that some processes on a machine with hyperthreading could "spy" on others, and also that hyperthreading didn't always improve performance on high end processors, the feature was turned off by default. But on single-user machines, or on servers where the CPU was likely to be shared by two processes that were both privileged anyway, it might make sense to re-enable it. But has this feature of the scheduler been maintained well enough for this to be a good idea? If not, would it worth looking into updating it so that FreeBSD runs well on the Atom? --Brett Glass as far as i know, just enabling smp will allow ht to function. also, i don't know if intel changed ht in the new atom processor, they could have. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org" ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: Status of hyperthreading in FreeBSD
"Netbooks" based on Intel's "Atom" microprocessor are turning into big hits this Christmas season. The Atom, a super-low-power x86 processor, is an "in-order" machine, which means that except for a few special cases it can spend a lot of time waiting for data to arrive when it encounters a cache miss. So, hyperthreading may make sense on this kind of processor as compared to one with out-of-order execution. Which raises a question: What's the status of FreeBSD's support for hyperthreading? for FreeBSD it's just like 2 processors. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: Status of hyperthreading in FreeBSD
Brett Glass wrote: > Which raises a question: What's the status of FreeBSD's support for > hyperthreading? As far as I know, after it was revealed that some > processes on a machine with hyperthreading could "spy" on others, and Yes, but that is a hardware problem which is independent of the operating system (it's present in all of them). > also that hyperthreading didn't always improve performance on high end > processors, the feature was turned off by default. But on single-user Yes, especially on the early Pentium 4 CPUs. This is also OS-independent. > machines, or on servers where the CPU was likely to be shared by two > processes that were both privileged anyway, it might make sense to > re-enable it. But has this feature of the scheduler been maintained well > enough for this to be a good idea? If not, would it worth looking into > updating it so that FreeBSD runs well on the Atom? It's as good as it can be on recent ULE2 scheduler. ULE2 has support for HTT but there's not much that can be done at the scheduler level as the Atom is single-socket, single-core CPU. Atom's HTT is actually pretty good - I saw up to 25% more performance simply by using multithreading in 7zip's compression benchmark (on WinXP, though). Of course, OTOH it uses about that much more transistors on the CPU die so it's not exactly free performance. signature.asc Description: OpenPGP digital signature
Re: Status of hyperthreading in FreeBSD
>> > as far as i know, just enabling smp will allow ht to function. also, i don't > know if intel changed ht in the new atom processor, they could have. >> is FreeBSD's smp special in some way that it would be the exception to the following statement. I know there was a lot of changes made in the new ULE2 scheduler maybe that is why? /* Hyper-threading relies on support in the operating system as well as the CPU. Conventional multiprocessor support is not enough to take advantage of hyper-threading.[1] For example, even though Windows 2000 supports multiple CPUs, Intel does not recommend that hyper-threading be enabled under that operating system. */ I found this in wikipedia at the following link http://en.wikipedia.org/wiki/Hyper-threading Sam Fourman Jr. Fourman Networks ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: Status of hyperthreading in FreeBSD
Atom's HTT is actually pretty good - I saw up to 25% more performance simply by using multithreading in 7zip's compression benchmark (on WinXP, though). Of course, OTOH it uses about that much more transistors on the CPU die so it's not exactly free performance. really that much? i thought maybe 1-2% (just 2 sets of registers). it would be better to put 2 much simpler cores in place of this one. or 100 ARM7 cores ;) (it would fit) ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
Re: Status of hyperthreading in FreeBSD
Sam Fourman Jr. wrote:
>> as far as i know, just enabling smp will allow ht to function. also, i don't
>> know if intel changed ht in the new atom processor, they could have.
> is FreeBSD's smp special in some way that it would be the exception to
> the following statement.
> I know there was a lot of changes made in the new ULE2 scheduler maybe
> that is why?
>
> /*
> Hyper-threading relies on support in the operating system as well as
> the CPU. Conventional multiprocessor support is not enough to take
> advantage of hyper-threading.[1] For example, even though Windows 2000
> supports multiple CPUs, Intel does not recommend that hyper-threading
> be enabled under that operating system.
> */
>
> I found this in wikipedia at the following link
> http://en.wikipedia.org/wiki/Hyper-threading
Yes, system respond variously to hyperthreading but it's mostly in two
areas:
a) Granularity of locking - systems with "big locks" like FreeBSD's
Giant was when HTT was new don't scale well in multi-CPU configurations
("logical" CPUs) and simply using HTT can expose and increase these
inefficiencies. Modern FreeBSD locking is "good enough" for 8 cores in
7.x and it's improving in 8.x.
b) Behaviour in multi-core (or multi-CPU) case when individual CPUs or
cores support HTT. This is a scheduler issue - if the scheduler isn't
aware that some logical CPU's are "fake" and some are not (i.e. if it
treats all of them equally) it could move processes or threads from one
CPU or CPU core to another when it would be much better to move it from
one "fake" (hyperthreaded) CPU to another within the same "real" CPU.
There are more similar issues here, but none of them (including those I
described) are applicable to Atom since a) locking in FreeBSD is good
enough for it in recent releases (even in 6.x) and b) there are only two
"fake" logical CPUs and they really can be treated equally.
Now, with Nehalem design (i7) the system can have a quad-core CPU
(actually, several of those) with each core supporting hyperthreading. A
system with 16 logical CPUs (2 x quadcore x HTT) isn't really strange
any more. The scheduler knows about HTT, so the issues under "a)" are
much more noticable.
signature.asc
Description: OpenPGP digital signature
Re: Status of hyperthreading in FreeBSD
Wojciech Puchar wrote: >> >> Atom's HTT is actually pretty good - I saw up to 25% more performance >> simply by using multithreading in 7zip's compression benchmark (on >> WinXP, though). Of course, OTOH it uses about that much more transistors >> on the CPU die so it's not exactly free performance. > > really that much? i thought maybe 1-2% (just 2 sets of registers). Screenshots are available :) I was also surprised because in this case both threads use the same algorithm with the same requirements on registers. It used to be (in the days of Pentium 4) that HTT would work best if the two threads used different sets of instructions and registers (e.g. one doing integer math and another doing floating point math). I guess they made more effort this time. signature.asc Description: OpenPGP digital signature
Hyperthreading not working on my 5.3 FreeBSD
Well the output of my dmesg command is only showing 1 processor , HT is enabled in bios , & working on windows XP on the same PC. what can be wrong ? is there anyway to enable it ? thanks *º¤., ¸¸,.¤º*¨¨¨*¤ Allah-hu-Akber*º¤., ¸¸,.¤º*¨¨*¤ God is the Greatest __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
