linux-kernel - Re: [PATCH -tip 1/3] introduce task_times() to replace task

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Message-ID: <1259231144.4273.27.camel@twins>
Date:	Thu, 26 Nov 2009 11:25:44 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Spencer Candland <spencer@...ehost.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Balbir Singh <balbir@...ibm.com>,
	Américo Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH -tip 1/3] introduce task_times() to replace
 task_{u,s}time() pair

On Thu, 2009-11-26 at 14:48 +0900, Hidetoshi Seto wrote:
> Functions task_{u,s}time() are called in pair in almost all
> cases.  However task_stime() is implemented to call task_utime()
> from its inside, so such paired calls run task_utime() twice.
> 
> It means we do heavy divisions (div_u64 + do_div) twice to get
> utime and stime which can be obtained at same time by one set
> of divisions.
> 
> This patch introduces a function task_times(*tsk, *utime, *stime)
> to retrieve utime and stime at once in better, optimized way.
> 
> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>

OK, the patch looks good, but it does not solve those non monotonic
times funnies that started all this, right?

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