Date: Fri, 17 Nov 2006 20:20:52 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Mike Galbraith <efault@gmx.de>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>, nickpiggin@yahoo.com.au,
       "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>
Subject: Re: [rfc patch] Re: sched: incorrect argument used in task_hot()
Message-ID: <20061117192052.GA23272@elte.hu>
References: <000201c70840$a4902df0$d834030a@amr.corp.intel.com> <1163782610.22574.59.camel@Homer.simpson.net>
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* Mike Galbraith <efault@gmx.de> wrote:

> One way to improve granularity, and eliminate the possibility of 
> p->last_run being > rq->timestamp_tast_tick, and thereby short 
> circuiting the evaluation of cache_hot_time, is to cache the last 
> return of sched_clock() at both tick and sched times, and use that 
> value as our reference instead of the absolute time of the tick.  It 
> won't totally eliminate skew, but it moves the reference point closer 
> to the current time on the remote cpu.
> 
> Looking for a good place to do this, I chose update_cpu_clock().

looks good to me - thus we will update the timestamp not only in the 
timer tick, but also upon every context-switch (when we acquire 
sched_clock() value anyway). Lets try this in -mm?

Acked-by: Ingo Molnar <mingo@elte.hu>

	Ingo
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