linux-kernel - Re: [tip:sched/urgent] sched: do not count frozen tasks toward load

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Message-ID: <20090410092048.GA30093@elf.ucw.cz>
Date:	Fri, 10 Apr 2009 11:20:48 +0200
From:	Pavel Machek <pavel@....cz>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	matthltc@...ibm.com, nigel@...onice.net, akpm@...ux-foundation.org,
	stable@...nel.org, tglx@...utronix.de, ntl@...ox.com, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/urgent] sched: do not count frozen tasks toward load

On Thu 2009-04-09 05:39:32, Nathan Lynch wrote:
> Commit-ID:  e3c8ca8336707062f3f7cb1cd7e6b3c753baccdd
> Gitweb:     http://git.kernel.org/tip/e3c8ca8336707062f3f7cb1cd7e6b3c753baccdd
> Author:     Nathan Lynch <ntl@...ox.com>
> AuthorDate: Wed, 8 Apr 2009 19:45:12 -0500
> Committer:  Ingo Molnar <mingo@...e.hu>
> CommitDate: Thu, 9 Apr 2009 07:37:02 +0200
> 
> sched: do not count frozen tasks toward load
> 
> Freezing tasks via the cgroup freezer causes the load average to climb
> because the freezer's current implementation puts frozen tasks in
> uninterruptible sleep (D state).
> 
> Some applications which perform job-scheduling functions consult the
> load average when making decisions.  If a cgroup is frozen, the load
> average does not provide a useful measure of the system's utilization
> to such applications.  This is especially inconvenient if the job
> scheduler employs the cgroup freezer as a mechanism for preempting low
> priority jobs.  Contrast this with using SIGSTOP for the same purpose:
> the stopped tasks do not count toward system load.
> 
> Change task_contributes_to_load() to return false if the task is
> frozen.  This results in /proc/loadavg behavior that better meets
> users' expectations.
> 
> Signed-off-by: Nathan Lynch <ntl@...ox.com>
> Acked-by: Andrew Morton <akpm@...ux-foundation.org>
> Acked-by: Nigel Cunningham <nigel@...onice.net>
> Tested-by: Nigel Cunningham <nigel@...onice.net>
> Cc: <stable@...nel.org>
> Cc: containers@...ts.linux-foundation.org
> Cc: linux-pm@...ts.linux-foundation.org
> Cc: Matt Helsley <matthltc@...ibm.com>
> LKML-Reference: <20090408194512.47a99b95@...atee.lan>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>

Acked-by: Pavel Machek <pavel@....cz>

-- 
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