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From: Ingo Molnar <mingo@kernel.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Matt Fleming <matt@codeblueprint.co.uk>,
	Mike Galbraith <mgalbraith@suse.de>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] sched: Make schedstats a runtime tunable that is disabled by default v4
Date: Wed, 3 Feb 2016 12:28:49 +0100	[thread overview]
Message-ID: <20160203112849.GB27850@gmail.com> (raw)
In-Reply-To: <1454497668-22297-1-git-send-email-mgorman@techsingularity.net>


* Mel Gorman <mgorman@techsingularity.net> wrote:

> Changelog since v3
> o Force enable stats during profiling and latencytop
> 
> Changelog since V2
> o Print stats that are not related to schedstat
> o Reintroduce a static inline for update_stats_dequeue
> 
> Changelog since V1
> o Introduce schedstat_enabled and address Ingo's feedback
> o More schedstat-only paths eliminated, particularly ttwu_stat
> 
> schedstats is very useful during debugging and performance tuning but it
> incurs overhead. As such, even though it can be disabled at build time,
> it is often enabled as the information is useful.  This patch adds a
> kernel command-line and sysctl tunable to enable or disable schedstats on
> demand. It is disabled by default as someone who knows they need it can
> also learn to enable it when necessary.
> 
> The benefits are workload-dependent but when it gets down to it, the
> difference will be whether cache misses are incurred updating the shared
> stats or not. [...]

Hm, which shared stats are those? I think we should really fix those as well: 
those shared stats should be percpu collected as well, with no extra cache misses 
in any scheduler fast path.

Thanks,

	Ingo

  reply	other threads:[~2016-02-03 11:29 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-03 11:07 [PATCH 1/1] sched: Make schedstats a runtime tunable that is disabled by default v4 Mel Gorman
2016-02-03 11:28 ` Ingo Molnar [this message]
2016-02-03 11:39   ` Mel Gorman
2016-02-03 12:49     ` Ingo Molnar
2016-02-03 13:32       ` Mel Gorman
2016-02-03 14:56         ` Mel Gorman
2016-02-03 11:51 ` Srikar Dronamraju

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