Re: hyperthreading....
On Mon, 2014-05-05 at 09:25 -0700, Carruth, Rusty wrote: > In my past experience, I had noticed that the BOGOMIPS reported on > (each of the) hyperthreading enabled CPUs was half that of the same > CPU with hyperthreading turned off. Which made me believe that the 2 > CPUs were effectively half the speed of the single one. (That is, if > single is 2 bogomips, then hyperthreaded it was 1 bogomips on each > CPU). The answer is "it's complicated." But in general processor designs have gone through a history of optimizing what is called "Instruction Level Parallelism." Basically this means if you have two instructions that are next to each other, one is an addition and the other a multiplication, and they don't need each other's value the processor will do them at the same time. This is pretty cool because more of the processor gets used at once. Then people realized you could put two multiplication units on and if there were two multiplies next to each other, both of those could be done at the same time and overall things were faster. But, the case quickly arose where there weren't two multiplications next to each other so you had part of the processor sitting idle. So, again trying to use the full CPU engineers looked to "Thread Level Parallelism" to try and find the additional multiply. Basically this means the CPU is aware of the second process and starts looking to fill the empty area of the processor's execution units with instructions from that second process. Is it faster? The answer is: "it depends." If you have two processes that are both constantly using the multiplication unit, no, you still run out of multiplication units. But if one is doing addition and the other multiplication then you'd have a processor that looked twice as fast! Reality is somewhere in between, but it depends on workload. Estimates I've seen have put it at a 20% speedup, but YMMV. Ted signature.asc Description: This is a digitally signed message part --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss
Re: hyperthreading....
First Gen Hyperthreading was interesting but the processors and corresponding front side bus's did not have enough bandwidth to utilize the technology correctly. the current rendition has far more bandwidth available and it is far more useful. In working with linux it is much better at using hyperthreading then windows is, due to its natural handling of parallel multitasking. I would suggest you enable it for more modern hardware (Core i series ect), but on really old school systems i would enable it if you have lots of little processes or a large process with a number of little processes on the side. On Mon, May 5, 2014 at 9:25 AM, Carruth, Rusty wrote: > In my past experience, I had noticed that the BOGOMIPS reported on (each > of the) hyperthreading enabled CPUs was half that of the same CPU with > hyperthreading turned off. Which made me believe that the 2 CPUs were > effectively half the speed of the single one. (That is, if single is 2 > bogomips, then hyperthreaded it was 1 bogomips on each CPU). > > > > Since I knew that Linux did a good job of true multitasking, I always > turned it off (assuming that part of the impetus for the whole thing was > that Windows did a TERRIBLE job of true multitasking (remember trying to do > ANYTHING else while doing a floppy format? Yeah, I thought you did J) so > that windows could tie up one of the 'CPUs' doing a floppy format (or > whatever) and still look responsive to the GUI using the other 'CPU'. > > > > So, I have to ask a few questions: > > > > 1 - does that slow 1.2GHz (SLOW? 1.2G? Wow, how times have changed!) play > back fine with hyperthreading turned off? > > 2 - if XBMC gives a 20% performance boost on a CPU that is running at half > the speed, is that really a performance boost overall? (I'm probably > missing something...) > > > > Just wondering J > > > > Rusty > > > > *From:* plug-discuss-boun...@lists.phxlinux.org [mailto: > plug-discuss-boun...@lists.phxlinux.org] *On Behalf Of *Bryan O'Neal > *Sent:* Sunday, May 04, 2014 9:48 PM > *To:* Main PLUG discussion list > *Subject:* Re: hyperthreading > > > > Short answer is that it is a way each physical core gets presented to the > OS as two logically cores. Through some well documented voodoo it increases > paralization for some work loads. Available on many Pentium systems since > the Pentium 4 but also requires comparable chipsets so some early systems > had processors that supported it but still could not use it. Mostly I see > it on Xoen systems > Some bios allow you to disable it. > > On May 4, 2014 9:35 PM, "Michael Havens" wrote: > > what is it and is it an option in a modern BIOS? > > I ask because I got an interesting message on another list othat I > participate in. > > [quote]Even though an AGP card may not support vdpau acceleration, a p4 > should be able to use the Nvidia driver to get some openGL 2D accelerated > output for XBMC. You should also have hyperthreading turned on in the BIOS, > so the system will see two CPU cores, as XMBC will take advantage of that > for maybe a 20% performance boost. My netbook, with a slow 1.2 GHz > hyperthreaded Intel Atom CPU and 945M graphics, is still able to play back > 720p h.264 encoded movies smoothly on MX 14. > > > Steve (finishing up the packaging of XBMC 13.0, which coincidently was > just released)[/quote] > > :-)~MIKE~(-: > > > --- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > > --- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > -- A mouse trap, placed on top of your alarm clock, will prevent you from rolling over and going back to sleep after you hit the snooze button. Stephen --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss
RE: hyperthreading....
In my past experience, I had noticed that the BOGOMIPS reported on (each of the) hyperthreading enabled CPUs was half that of the same CPU with hyperthreading turned off. Which made me believe that the 2 CPUs were effectively half the speed of the single one. (That is, if single is 2 bogomips, then hyperthreaded it was 1 bogomips on each CPU). Since I knew that Linux did a good job of true multitasking, I always turned it off (assuming that part of the impetus for the whole thing was that Windows did a TERRIBLE job of true multitasking (remember trying to do ANYTHING else while doing a floppy format? Yeah, I thought you did J) so that windows could tie up one of the ‘CPUs’ doing a floppy format (or whatever) and still look responsive to the GUI using the other ‘CPU’. So, I have to ask a few questions: 1 – does that slow 1.2GHz (SLOW? 1.2G? Wow, how times have changed!) play back fine with hyperthreading turned off? 2 – if XBMC gives a 20% performance boost on a CPU that is running at half the speed, is that really a performance boost overall? (I’m probably missing something…) Just wondering J Rusty From: plug-discuss-boun...@lists.phxlinux.org [mailto:plug-discuss-boun...@lists.phxlinux.org] On Behalf Of Bryan O'Neal Sent: Sunday, May 04, 2014 9:48 PM To: Main PLUG discussion list Subject: Re: hyperthreading Short answer is that it is a way each physical core gets presented to the OS as two logically cores. Through some well documented voodoo it increases paralization for some work loads. Available on many Pentium systems since the Pentium 4 but also requires comparable chipsets so some early systems had processors that supported it but still could not use it. Mostly I see it on Xoen systems Some bios allow you to disable it. On May 4, 2014 9:35 PM, "Michael Havens" wrote: what is it and is it an option in a modern BIOS? I ask because I got an interesting message on another list othat I participate in. [quote]Even though an AGP card may not support vdpau acceleration, a p4 should be able to use the Nvidia driver to get some openGL 2D accelerated output for XBMC. You should also have hyperthreading turned on in the BIOS, so the system will see two CPU cores, as XMBC will take advantage of that for maybe a 20% performance boost. My netbook, with a slow 1.2 GHz hyperthreaded Intel Atom CPU and 945M graphics, is still able to play back 720p h.264 encoded movies smoothly on MX 14. Steve (finishing up the packaging of XBMC 13.0, which coincidently was just released)[/quote] :-)~MIKE~(-: --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss
Re: hyperthreading....
Short answer is that it is a way each physical core gets presented to the OS as two logically cores. Through some well documented voodoo it increases paralization for some work loads. Available on many Pentium systems since the Pentium 4 but also requires comparable chipsets so some early systems had processors that supported it but still could not use it. Mostly I see it on Xoen systems Some bios allow you to disable it. On May 4, 2014 9:35 PM, "Michael Havens" wrote: > what is it and is it an option in a modern BIOS? > I ask because I got an interesting message on another list othat I > participate in. > [quote]Even though an AGP card may not support vdpau acceleration, a p4 > should be able to use the Nvidia driver to get some openGL 2D accelerated > output for XBMC. You should also have hyperthreading turned on in the BIOS, > so the system will see two CPU cores, as XMBC will take advantage of that > for maybe a 20% performance boost. My netbook, with a slow 1.2 GHz > hyperthreaded Intel Atom CPU and 945M graphics, is still able to play back > 720p h.264 encoded movies smoothly on MX 14. > > Steve (finishing up the packaging of XBMC 13.0, which coincidently was > just released)[/quote] > :-)~MIKE~(-: > > --- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss
hyperthreading....
what is it and is it an option in a modern BIOS? I ask because I got an interesting message on another list othat I participate in. [quote]Even though an AGP card may not support vdpau acceleration, a p4 should be able to use the Nvidia driver to get some openGL 2D accelerated output for XBMC. You should also have hyperthreading turned on in the BIOS, so the system will see two CPU cores, as XMBC will take advantage of that for maybe a 20% performance boost. My netbook, with a slow 1.2 GHz hyperthreaded Intel Atom CPU and 945M graphics, is still able to play back 720p h.264 encoded movies smoothly on MX 14. Steve (finishing up the packaging of XBMC 13.0, which coincidently was just released)[/quote] :-)~MIKE~(-: --- PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org To subscribe, unsubscribe, or to change your mail settings: http://lists.phxlinux.org/mailman/listinfo/plug-discuss
