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Date: Fri, 8 Aug 2014 10:38:53 +0200 From: Ingo Molnar <mingo@...nel.org> To: Rik van Riel <riel@...hat.com> Cc: Fengguang Wu <fengguang.wu@...el.com>, Dave Hansen <dave.hansen@...el.com>, Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>, lkp@...org, Peter Zijlstra <peterz@...radead.org> Subject: Re: [sched/numa] 096aa33863a: -21.4% hackbench.throughput, -20.2% netperf.Throughput_Mbps * Rik van Riel <riel@...hat.com> wrote: > On 08/07/2014 06:53 AM, Fengguang Wu wrote: > > Hi Rik, > > > > We noticed the below performance regression in commit > > 096aa33863a5e48de52d2ff30e0801b7487944f4 ("sched/numa: Decay > > ->wakee_flips instead of zeroing") > > > > b1ad065e65f5610 096aa33863a5e48de52d2ff30 testbox/testcase/testparams > > --------------- ------------------------- --------------------------- > > 122361 ± 0% -21.4% 96140 ± 0% lkp-snb01/hackbench/50%-process-pipe > > 122361 ± 0% -21.4% 96140 ± 0% TOTAL hackbench.throughput > > I guess the performance of that benchmark depends on it > "slipping under the wire" after each time the kernel > zeroes out ->wakee_flips. > > Depending on repeatedly pulling the wakee back to the same > node as the waker suggests something else in the kernel may > be pulling the wakee to another place in the system repeatedly, > as well, just at a lower frequency (load balancer?). > > I have also noticed that select_idle_sibling often fails to > find an idle sibling within the LLC domain, even when it > exists. Fixing that bug sometimes results in lower performance. > > It appears that some of the performance results of the scheduler > appear on the code acting in an opposite way to its documented > intention. > > It may be best to revert 096aa33863a for now... Mind sending a revert patch, with an explanation, a Reported-by, etc? Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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