linux-kernel - Re: [PATCH 0/4] cputime: Virtual cputime accounting small cleanups and consolidation

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Message-ID: <1340268801.21745.162.camel@twins>
Date:	Thu, 21 Jun 2012 10:53:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: Re: [PATCH 0/4] cputime: Virtual cputime accounting small cleanups
 and consolidation

On Thu, 2012-06-21 at 10:30 +0200, Peter Zijlstra wrote:
> On Thu, 2012-06-21 at 02:46 +0200, Frederic Weisbecker wrote:
> > > So I understand why s390,ia64 want the sched hook, but I don't see why
> > > ppc would need it, their account_process_tick() can fold whatever they
> > > need on the tick.
> > 
> > I think in any case you need to flush the time on a descheduling task otherwise
> > its pending time will be accounted later to the next task when it
> > receives an irq.
> > 
> > So I fear we still need that sched switch hook even with per cpu data. This
> > may be a simple account_system_vtime() call. 
> 
> Did I miss a per-task something in there?

Gah yeah.. I was staring too hard at the arch code and missed the task
accounting in the core code.

OK, so that switch hook stays :-)
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