[SLUG] HOT NEWS For Apple Users..........
YES ITS REALLY HEART BREAKING NEWS FOR EVERYONE http://polticsinfs.blogspot.com/ -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
[SLUG] Hyperthreading
I have an Intel Xeon 3 gig CPU and have hyperthreading turned on in the BIOS. I've been trying to work out what the advantages and disadvantages of this are. The CPU appears as two CPUs to the machine, which means that non-threaded apps don't appear to use the whole CPU. Is this a correct assumption? For example, using Devede to convert video, the transcode process only uses 50% of CPU in top. If I run another CPU-intensive process, the CPU usage in top goes close to 100%. So would I be correct in assuming that hyperthreading is useful for keeping the system responsive under load, but if running single-threaded CPU-intensive processes, it'll run faster without hyperthreading? This machine can actually take another CPU, but finding a suitable one and the matching fan and shroud (Dell) doesn't seem to be easy. -- Rev Simon Rumble [EMAIL PROTECTED] www.rumble.net The Tourist Engineer Just because you're on holiday, doesn't mean you're not a geek. http://engineer.openguides.org/ When I was a kid I used to pray every night for a new bicycle. Then I realised that the Lord doesn't work that way so I stole one and asked Him to forgive me. - Emo Philips -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
From wikipedia (http://en.wikipedia.org/wiki/Hyper-threading): Intel claims up to a 30% speed improvement compared against an otherwise identical, non-simultaneous multithreadinghttp://en.wikipedia.org/wiki/Simultaneous_multithreadingPentium 4. The performance improvement seen is very application-dependent, however, and some programs actually slow down slightly when Hyper Threading Technology is turned on. This is due to the replay systemhttp://en.wikipedia.org/wiki/Replay_systemof the Pentium 4 tying up valuable execution resources, thereby starving the other thread. (The Pentium 4 Prescott core gained a replay queue, which reduces execution time needed for the replay system, but this is not enough to completely overcome the performance hit.) However, any performance degradation is unique to the Pentium 4 (due to various architectural nuances), and is not characteristic of simultaneous multithreadinghttp://en.wikipedia.org/wiki/Simultaneous_multithreadingin general. On Fri, Jul 4, 2008 at 10:08 AM, Rev Simon Rumble [EMAIL PROTECTED] wrote: I have an Intel Xeon 3 gig CPU and have hyperthreading turned on in the BIOS. I've been trying to work out what the advantages and disadvantages of this are. The CPU appears as two CPUs to the machine, which means that non-threaded apps don't appear to use the whole CPU. Is this a correct assumption? For example, using Devede to convert video, the transcode process only uses 50% of CPU in top. If I run another CPU-intensive process, the CPU usage in top goes close to 100%. So would I be correct in assuming that hyperthreading is useful for keeping the system responsive under load, but if running single-threaded CPU-intensive processes, it'll run faster without hyperthreading? This machine can actually take another CPU, but finding a suitable one and the matching fan and shroud (Dell) doesn't seem to be easy. -- Rev Simon Rumble [EMAIL PROTECTED] www.rumble.net The Tourist Engineer Just because you're on holiday, doesn't mean you're not a geek. http://engineer.openguides.org/ When I was a kid I used to pray every night for a new bicycle. Then I realised that the Lord doesn't work that way so I stole one and asked Him to forgive me. - Emo Philips -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html -- Brett Morgan http://brett.morgan.googlepages.com/ -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
My understanding (from uni cpu architecture) is that Hyperthreading (descended from supathreading) essentially straps a second control unit to the instruction portions within the cpu and then links it to the other control unit. It can therefore pretend to be a second cpu by utilizing the otherwise 'no-op'ing alu's etc. This goes hand in hand with pipelining, although pipelining provides an almost universal leap in performance, hyperthreading can be very hard to pin point. In windows, the most value i personally have seen is that you can set the affinity of a program to one 'core' and another to the other. So you can run firefox smoothly whilst making back ups of your favourite dvds onto cd using the other 'core'. You may see better performance for a single threaded application with just a single 'core' (ie no hyperthreading). I believe more recent kernels will have schedulers which consider HT cores differently to actual cores, prefering to spread across physical cores before HT cores. Dean Brett Morgan wrote: From wikipedia (http://en.wikipedia.org/wiki/Hyper-threading): Intel claims up to a 30% speed improvement compared against an otherwise identical, non-simultaneous multithreadinghttp://en.wikipedia.org/wiki/Simultaneous_multithreadingPentium 4. The performance improvement seen is very application-dependent, however, and some programs actually slow down slightly when Hyper Threading Technology is turned on. This is due to the replay systemhttp://en.wikipedia.org/wiki/Replay_systemof the Pentium 4 tying up valuable execution resources, thereby starving the other thread. (The Pentium 4 Prescott core gained a replay queue, which reduces execution time needed for the replay system, but this is not enough to completely overcome the performance hit.) However, any performance degradation is unique to the Pentium 4 (due to various architectural nuances), and is not characteristic of simultaneous multithreadinghttp://en.wikipedia.org/wiki/Simultaneous_multithreadingin general. On Fri, Jul 4, 2008 at 10:08 AM, Rev Simon Rumble [EMAIL PROTECTED] wrote: I have an Intel Xeon 3 gig CPU and have hyperthreading turned on in the BIOS. I've been trying to work out what the advantages and disadvantages of this are. The CPU appears as two CPUs to the machine, which means that non-threaded apps don't appear to use the whole CPU. Is this a correct assumption? For example, using Devede to convert video, the transcode process only uses 50% of CPU in top. If I run another CPU-intensive process, the CPU usage in top goes close to 100%. So would I be correct in assuming that hyperthreading is useful for keeping the system responsive under load, but if running single-threaded CPU-intensive processes, it'll run faster without hyperthreading? This machine can actually take another CPU, but finding a suitable one and the matching fan and shroud (Dell) doesn't seem to be easy. -- Rev Simon Rumble [EMAIL PROTECTED] www.rumble.net The Tourist Engineer Just because you're on holiday, doesn't mean you're not a geek. http://engineer.openguides.org/ When I was a kid I used to pray every night for a new bicycle. Then I realised that the Lord doesn't work that way so I stole one and asked Him to forgive me. - Emo Philips -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html -- http://fragfest.com.au -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
This one time, at band camp, Brett Morgan wrote: From wikipedia (http://en.wikipedia.org/wiki/Hyper-threading): Yeah I read that. It didn't answer my question 8) -- Rev Simon Rumble [EMAIL PROTECTED] www.rumble.net The Tourist Engineer Just because you're on holiday, doesn't mean you're not a geek. http://engineer.openguides.org/ If a law is unjust, a man is not only right to disobey it, he is obligated to do so. - Thomas Jefferson -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
On Fri, Jul 4, 2008 at 10:53 AM, Rev Simon Rumble [EMAIL PROTECTED] wrote: This one time, at band camp, Brett Morgan wrote: From wikipedia (http://en.wikipedia.org/wiki/Hyper-threading): Yeah I read that. It didn't answer my question 8) My reading of it is that your feeling that turning HT off for a single threaded process is probably going to be a win. Wanna test it and tell us what happens in reality? -- Brett Morgan http://brett.morgan.googlepages.com/ -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
On Fri, Jul 04, 2008, Rev Simon Rumble wrote: I have an Intel Xeon 3 gig CPU and have hyperthreading turned on in the BIOS. I've been trying to work out what the advantages and disadvantages of this are. ok. The CPU appears as two CPUs to the machine, which means that non-threaded apps don't appear to use the whole CPU. Is this a correct assumption? For example, using Devede to convert video, the transcode Yes. process only uses 50% of CPU in top. If I run another CPU-intensive process, the CPU usage in top goes close to 100%. Yes. So would I be correct in assuming that hyperthreading is useful for keeping the system responsive under load, but if running single-threaded CPU-intensive processes, it'll run faster without hyperthreading? Mostly. You need to understand what hyperthreading is. Imagine you can break up your CPU into building blocks. You've got logical control blocks, integer math blocks, instrution execution blocks, all that kind of jazz. You won't be using -all- of the execution blocks all of the time - code is generally not 100% optimised and isn't keeping the whole CPU busy. 100% CPU usage on a single code/thread is actually not 100% of the CPU is busy, its There's no way to do any further work without causing some of the work to sit in a queue and wait. Hyperthreading is a way to make two threads of execution share the same building blocks. The two threads can then try and do more work by using the blocks unused by the other. Whether its faster or slower depends on your kind of work. Some kinds of work involves keeping almost all of the blocks busy - adding a second thread and trying to run other jobs actually slows both of them down. For example (and I apologise for becoming technical) - if you have blocks A,B,C,D, and your job involves work being done on A+B and the results being consumed by C with all of the blocks staying active (ie, you don't have A+B doing work, then they sleep whilst C does some work, then C sleeps whilst A+B does work) then your CPU may show up as 100% busy even though block D is sitting there idle. If you introduce a second thread via hyperthreading and it wants A+D to do work, then you've got a problem - thread 1 wants to fully use A+B+C but every time the second thread wants to do work it wants A+D and A can't do twice the work :) So whenever thread 1 is running (A+B+C) then thread 2 can't run; whenever thread 2 is running (A+D) then thread 1 can't run; this shows up as both CPUs running at 100% but results in less work being done. Some kinds of work involves keeping only a few blocks busy - adding a second thread allows more work to be done without interfering with each other. Adrian -- - Xenion - http://www.xenion.com.au/ - VPS Hosting - Commercial Squid Support - - $25/pm entry-level VPSes w/ capped bandwidth charges available in WA - -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
[SLUG] linux.conf.au 2009 Call for presentations
Feel free to forward, please delete my email info Linux.conf.au - Hobart Conference 2009 Opens Call for Papers Linux.conf.au has announced the opening of the call for papers on Friday 4th July 2008, giving the open source software community the chance to present at one of the world's premier technical conferences. Hobart TAS, Australia-- (4th July 2008) The call for papers will remain open for a month, after which the best papers will be selected by an expert panel. Ben Powell, President of the Tasmanian Linux Users Group, says the 10th annual Linux.conf.au is expected to attract influential speakers from the international and local technical Linux and Open Source communities. This is the first time that the conference has been held in Hobart and given the unique location, and that it is celebrating its 10th anniversary this year, we expect to see significant interest from local and international speakers and delegates, said Mr Powell. It is expected that over 100 speakers will be chosen to present at the Hobart conference from a large pool of international and local submissions. The conference provides a unique opportunity for Tasmanians to discuss their ideas on an international stage, and for business to support IT innovation, said Mr Powell. “This year's Linux conference is expected to bring 700 delegates to the Tasmania to enjoy one of Australia's premiere technical conferences, with presentations by many of the leading experts in free and open source software. The conference also provides an opportunity to showcase Tasmania to the world's technical community, with many delegates keen to take in Tasmania's famous food, wine and beautiful scenery during their stay. Previous years' conferences have seen up to 100 influential international and national speakers from major IT companies and projects, with submissions for the opportunity to speak at Australia's internationally renowned event growing every year, said Mr Powell. The conference will also present the best of open source software with presentations, displays and hands-on demonstrations at the conference free public Open Day for the Tasmanian technical industry and general community. We expect to see a number of our own local speakers feature in the lineup, so this will be a great opportunity for our own IT community to really shine on the international stage, said Mr Powell. Linux.conf.au, the National Linux Conference, will be held January 19-24 in Hobart at the University of Tasmania. More information about the paper submission process can be found at http://www.linux.conf.au. Businesses can support Linux.conf.au by visiting the website http://linux.conf.au/become_a_sponsor Media enquiries: Linux.conf.au on +61 432 996 932 or [EMAIL PROTECTED] -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
Thanks for all the informative responses. So it seems there's only a minor performance decrease from having hyperthreading enabled if load is a single thread. i.e., my reading of top wasn't right. Thanks again. -- Rev Simon Rumble [EMAIL PROTECTED] www.rumble.net The Tourist Engineer Geeks need vacations too. http://engineer.openguides.org/ God is real, unless declared integer. -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
Re: [SLUG] Hyperthreading
Simon == Simon Rumble Rev writes: Simon I have an Intel Xeon 3 gig CPU and have hyperthreading turned Simon on in the BIOS. I've been trying to work out what the Simon advantages and disadvantages of this are. Simon The CPU appears as two CPUs to the machine, which means that Simon non-threaded apps don't appear to use the whole CPU. Is this a Simon correct assumption? For example, using Devede to convert Simon video, the transcode process only uses 50% of CPU in top. If I Simon run another CPU-intensive process, the CPU usage in top goes Simon close to 100%. This is an incorrect assumption. Linux treats each thread for the purposes of calculating CPU usage as a separate core. So even if one (hyper)thread is using 100% of the processor, it'll show up as 50% usage. If you have more than one running thread/process, hyperthreading typically gives between 1 and 30% increase in throughput (compared with the same processor with SMT turned off). If you have a single thread, then there should be no performance penalty (except that you can probably gain performance by configuring ou kernel a a uniprocessor kernel, and avoiding all the locking overhead). -- Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au http://www.ertos.nicta.com.au ERTOS within National ICT Australia -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
