linux-kernel - Re: [PATCH 2/2] sched: Lower chances of cputime scaling overflow

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Message-ID: <CAFTL4hwDZG8eeX3r2-JNosN-axmmpfCTGwRsGSptQSi+3e0y5Q@mail.gmail.com>
Date:	Wed, 13 Mar 2013 18:53:31 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] sched: Lower chances of cputime scaling overflow

2013/3/12 Frederic Weisbecker <fweisbec@...il.com>:
> 2013/3/7 Stanislaw Gruszka <sgruszka@...hat.com>:
>>> +     } else if (!total) {
>>>               stime = rtime;
>>
>> I would prefer stime = rtime/2 (hence utime will be rtime/2 too), but this
>> is not so important.
>
> I can do that.

I eventually kept it that way. Reason is that tasks always spend at
least a bit of time in the kernel when they are scheduled for the
first time. But they might never go to userspace, as in kernel
threads. So I prefer to stuff everything in stime by default. Having
(total == 0 && rtime != 0) should only happen for very low values of
rtime anyway.
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