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

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Message-ID: <20180702152106.GD533219@devbig577.frc2.facebook.com>
Date:   Mon, 2 Jul 2018 08:21:06 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Xunlei Pang <xlpang@...ux.alibaba.com>,
        Ingo Molnar <mingo@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion

Hello, Peter.

On Tue, Jun 26, 2018 at 05:49:08PM +0200, Peter Zijlstra wrote:
> Well, no, because the Changelog is incomprehensible and the patch
> doesn't really have useful comments, so I'll have to reverse engineer
> the entire thing, and I've just not had time for that.

Just as an additional data point, we also sometimes see artifacts from
cpu_adjust_time() in the form of per-task user or sys time getting
stuck for some period (in extreme cases for over a minute) while the
application isn't doing anything differently.  We're telling the users
that it's an inherent sampling artifact but it'd be nice to improve it
if possible without adding noticeable overhead.  No idea whether this
patch's approach is a good one tho.

Thanks.

-- 
tejun