Author: Robert Hyatt
Date: 08:22:58 09/17/03
Go up one level in this thread
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 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
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.