Author: Robert Hyatt
Date: 13:03:09 09/17/03
Go up one level in this thread
On September 17, 2003 at 14:54:41, Vincent Diepeveen wrote: >On September 17, 2003 at 14:47:49, Robert Hyatt wrote: > >lower clocked opterons are like $300, so i am pretty sure there is a big demand >already. No there isn't, because for single and dual machines, the NUMA issue can pretty well be ignored. There are not many 16-way boxes available at the present, which means the NUMA issue is a ways off from becoming a real issue. But it will eventually. There are a few dual opteron machines around, for sure. But I'm not seeing much beyond that yet... > > > >>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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