Author: Robert Hyatt
Date: 11:47:49 09/17/03
Go up one level in this thread
On September 17, 2003 at 12:11:59, Vincent Diepeveen wrote: >On September 17, 2003 at 11:22:58, Robert Hyatt wrote: > >>On September 16, 2003 at 22:30:47, Vincent Diepeveen wrote: >> >>>On September 15, 2003 at 14:16:38, Robert Hyatt wrote: >>> >>>>On September 15, 2003 at 13:18:28, Gian-Carlo Pascutto wrote: >>>> >>>>>On September 14, 2003 at 12:52:54, Sietel Monic wrote: >>>>> >>>>>>My friend runs dual proccessors using hyperthreading so gets 4 threads, I know >>>>>>this is bad for chess. Just dont know why >>>>> >>>>>This is ok. Running with 2 threads on a dual processor with hyperthreading >>>>>enabled is _not_, unless you're running Linux 2.4.x or Windows Server 2003. >>> >>>You sure of this bob? >> >>I am certain. I have duals all over the place, running 2.4.20 and 2.4.21 (I > >Does that say 2.4.20-NUMA I don't compile with NUMA kernel option because I don't have any NUMA boxes. However, the -NUMA doesn't mean anything. You can compile a NUMA kernel and not have the -NUMA extension, and vice-versa... > >or does it only say 2.4.20 x86 ? > >But in general i agree. i find the linux OS as a whole a joke at NUMA machines. >And kernel 2.6 won't be much better either i bet. As I said before, there is presently very little demand for NUMA linux support. As the demand grows, the O/S sophistication will grow with it, just as SMP did. Original Linux had no SMP support either. Until the demand was formed as cheap duals and sorta-cheap quads came along later. Once the opteron is readily availble in cheaper configurations, NUMA support will take off... > >>did say I had not tested 2.4.22 yet). Also, your question is in the wrong >>place. I didn't write the above. GCP did. I responded to it (the response >>appears below).. >> >> >> >> >>> >>>QUADopteron:/diep/latency # uname -a >>>Linux QUADopteron 2.4.19-NUMA #3 SMP Wed Jul 2 18:34:37 CDT 2003 x86_64 unknown >>> >>>Perhaps all you need is a special extension to the kernel. > >>We are talking about hyper-threading. 4 logical processors with two real >>processors. What are you talking about? The opteron is not hyper-threaded. >>The issue is that the O/S has to recognize that with only two runnable processes >>on a dual-cpu hyper-threaded machine, it needs to run each process on a >>different physical processor for max performance, rather than running both on >>two logical processors that are on the same physical processor, which would >>run much slower. >> >> >>> >>>>Linux 2.4.x won't cut it either. I use 2.4.21 and it is _not_ SMT-aware. IE >>>>it will certainly recognize 4 processors, but it doesn't realize that if there >>>>are just two computational tasks to run, they should be run on two physical >>>>processors. 2.4 just runs them on any two logical processors. When the two >>>>logical processors are on one physical processor, this performs poorly. Ingo >>>>Molnar did a scheduler that addresses this (or maybe Rick did it). And it works >>>>well (it has two run queues, one for each physical procesor, rather than four, >>>>one for each logical processor.) But that isn't in mainstream 2.4 yet (I have >>>>not looked at 2.4.22 closely so it _could_ be there). >>>> >>>>> >>>>>-- >>>>>GCP
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