Subject: Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen
 tasks really
From: Nathan Lynch <ntl@pobox.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Helsley <matthltc@us.ibm.com>, Thomas Gleixner <tglx@linutronix.de>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>, Rafael Wysocki <rjw@sisk.pl>,
       Ingo Molnar <mingo@elte.hu>, Nigel Cunningham <nigel@tuxonice.net>,
       stable@kernel.org, containers@lists.linux-foundation.org,
       linux-pm@lists.linux-foundation.org
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Date: Fri, 17 Jul 2009 15:55:34 -0500
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On Fri, 2009-07-17 at 18:47 +0200, Peter Zijlstra wrote:
> On Fri, 2009-07-17 at 08:22 -0700, Matt Helsley wrote:
> 
> > The job scheduler in question does not use FROZEN as a transient state and
> > does not use checkpoint/restart at all since c/r is still a work in progress.

Right, the job scheduler uses the cgroup freezer as a mechanism to
preempt a low priority job for a higher priority job.  (It had used
SIGSTOP in the past.)  So in this scenario a frozen cgroup may remain in
that state for a while.  Load average is consulted as a measure of
system utilization.

> > Even when used for power management it seems wrong to count frozen tasks
> > towards the loadavg since they aren't using CPU time or waiting for IO.
> 
> You're abusing it for _WHAT_?

I think Matt was referring to system-wide suspend/resume/hibernate, not
a behavior of the job scheduler, if that's your concern.


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