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

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Message-ID: <20180709104759.GJ2476@hirez.programming.kicks-ass.net>
Date:   Mon, 9 Jul 2018 12:47:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     xunlei <xunlei.pang@...il.com>
Cc:     Xunlei Pang <xlpang@...ux.alibaba.com>,
        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 Thu, Jul 05, 2018 at 09:58:50PM +0800, xunlei wrote:
> It is rtime < utime + stime, that is the imprecise tick-based run time
> may be larger than precise sum_exec_runtime scheduler-based run time, it
> can happen with some frequent run-sleep patterns.

You're still comparing two values that should not be compared. utime +
stime is not a run-time. You _CANNOT_ compare to rtime and doing so
means you're still not getting it.