linux-kernel - Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen tasks really

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Date:	Fri, 17 Jul 2009 15:55:34 -0500
From:	Nathan Lynch <ntl@...ox.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Matt Helsley <matthltc@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rafael Wysocki <rjw@...k.pl>, Ingo Molnar <mingo@...e.hu>,
	Nigel Cunningham <nigel@...onice.net>, stable@...nel.org,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen
 tasks really

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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