Messages in this thread | | | Date | 27 Apr 2004 23:03:52 +0200 | Date | Tue, 27 Apr 2004 23:03:52 +0200 | From | Andi Kleen <> | Subject | Re: sched_domains and Stream benchmark |
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On Tue, Apr 27, 2004 at 09:47:19AM -0700, Darren Hart wrote: > On Mon, 2004-04-26 at 19:33, Andi Kleen wrote: > > > I noticed your binary ran with N=2000000 which is only sufficient for a > > > 2 proc 1 MB cache opteron box according to the documentation on the > > > > It does not seem to make any difference. > > I was under the impression you didn't change the N value (array size) > and ran the benchmark with someone else's precompiled binaries (the ones > you sent me). Did you have two binaries with different array sizes
Correct. I always used 2000000. But it did not seem to make any difference in showing the scheduler issues even when going to 4 CPUs.
(there were some fluctuations, but much less than the 25% you reported)
> > > stream faq. I also noticed wide variation in results (25% or so) when > > > running with 4 threads on a 4 proc opteron on linux-2.6.5-mm5. Can you > > > provide me with the specs of the system you ran your tests on? > > > > Yes, mm5 is still broken because it has the "tuned to numasaurus" numa > > scheduler. Run it on a standard (non mm*) kernel or with Ingo's early > > load balance patch. > > I ran it on 2.6.5, 2.6.5-mm5, and 2.6.5-mm5-flat-domains trying to > reproduce the results you found (including the poor performance of > virgin and mm) so that I can have some context while analyzing the > sched_domains topology on x86_64 and its effects on performance. So > that I can see where the differences lie in our tests, could you please > provide some of the specs of the system you ran on, such as number of > procs, cache size, and amount of RAM.
I saw the issue on a wide range of systems, ranging from 2 CPUs to 4 CPUs. All hard enough per CPU memory to fit the benchmark.
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