Author: Vincent Diepeveen
Date: 11:54:41 09/17/03
Go up one level in this thread
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. >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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