linux-kernel - Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion

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Message-ID: <20180705104632.GE2494@hirez.programming.kicks-ass.net>
Date:   Thu, 5 Jul 2018 12:46:32 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Xunlei Pang <xlpang@...ux.alibaba.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion

On Wed, Jun 27, 2018 at 08:22:42PM +0800, Xunlei Pang wrote:
> tick-based whole utime is utime_0, tick-based whole stime
> is stime_0, scheduler time is rtime_0. 

> For a long time, the process runs mainly in userspace with
> run-sleep patterns, and because two different clocks, it
> is possible to have the following condition:
>   rtime_0 < utime_0 (as with little stime_0)

I don't follow... what?

Why are you, and why do you think it makes sense to, compare rtime_0
against utime_0 ?

The [us]time_0 are, per your earlier definition, ticks. They're not an
actual measure of time. Do not compare the two, that makes no bloody
sense.