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Date: Fri, 29 Feb 2008 17:04:08 +0100 From: Ingo Molnar <mingo@...e.hu> To: "Carlos R. Mafra" <crmafra2@...il.com> Cc: ray-lk@...rabbit.org, linux-kernel@...r.kernel.org Subject: Re: Interactivity issue in 2.6.25-rc3 (on-list) * Carlos R. Mafra <crmafra2@...il.com> wrote: > Is it an scheduler anomaly if 'se.wait_max' is bigger than 40 msecs > for _any_ of the processes which appear in the debug script log? In > other words, is the scheduler mathematically build to not allow > latencies higher than 40 msecs? it is definitely an anomaly if it's bigger than 40 msecs if you clear all stats via cfs-debug-info-clear.sh and the large latencies appear after that. You can force it to go above 40 msecs if you run more than say 40 CPU hogs in parallel, so it's not "mathematical", but you should never see large latencies under normal workloads - and that includes almost everything but "insanely high" workloads. and obviously, even if you only 'feel' long delays that's too an anomaly by definition, no matter what the scripts say about it. It might even be a scheduler anomaly as well: for example if the scheduler clock has an anomaly - on which the delay statistics are based too. generally, latencytop gives a pretty good idea about where app delays come from. (As a second-level mechanism, in sched-devel.git you can try the latency tracer.) 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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