Messages in this thread | | | Subject | Re: hackbench regression with kernel 2.6.32-rc1 | From | "Zhang, Yanmin" <> | Date | Wed, 28 Oct 2009 17:29:01 +0800 |
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On Tue, 2009-10-27 at 15:42 +0100, Mike Galbraith wrote: > On Tue, 2009-10-27 at 16:03 +0800, Zhang, Yanmin wrote: > > On Fri, 2009-10-16 at 13:06 +0200, Mike Galbraith wrote: > > > On Tue, 2009-10-13 at 11:12 +0800, Zhang, Yanmin wrote: > > > > > > > NEXT_BUDDY has no help on volanoMark and tbench. > > > > > > Can you try the patch below please? It does tries to preserve buddy > > > affinity where possible, and mitigates over-preemption by strengthening > > > buddies a bit. It improves vmark here by ~7%. > > I ran some benchmarks against 2.6.32-rc1+Peter_2_patches+below_patch. > > Below result is against 2.6.32-rc1. > > hackbench result has about 10% improvement on stoakley (2*4 cores) and > > tigerton (4*4 cores). > > tbench still has about 5% regression on stoakley and tigerton. > > VolanoMark has 33% regression on tigerton, but has 2% improvement on stoakley. > > > > I also ran the benchmarks against the latest tips/master and got the similiar > > results like above testing. > > > > The testing against tips on Nehalem machine didn't show much improvement/regression. > > Thanks for the testing. Your results suggest that I should revive the > mark buddies whether you use them or not idea. > > -Mike I'm investigating 5% tbench regression on Nehalem machine. perf_counter shows select_task_rq_fair consumes about 5% cpu time with 2.6.32-rc1 while it consumes less than 0.5% with 2.6.31.
Patch c88d5910890 has comments to explain it, but I still can't understand why to add complicated balance logic when selecting task rq.
I will check which section in function select_task_rq_fair consumes so much time.
Yanmin
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