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Date: Thu, 30 Mar 2017 16:18:17 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>, Rik van Riel <riel@redhat.com>,
        Luiz Capitulino <lcapitulino@redhat.com>,
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        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [BUG nohz]: wrong user and system time accounting
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On Thu, Mar 30, 2017 at 09:59:54PM +0800, Wanpeng Li wrote:
> 2017-03-30 21:38 GMT+08:00 Frederic Weisbecker <fweisbec@gmail.com>:
> > If it works, we may want to take that solution, likely less performance sensitive
> > than using sched_clock(). In fact sched_clock() is fast, especially as we require it to
> > be stable for nohz_full, but using it involves costly conversion back and forth to jiffies.
> 
> So both Rik and you agree with the skew tick solution, I will try it
> tomorrow. Btw, if we should just add random offset to the cpu in the
> nohz_full mode or add random offset to all cpus like the codes above?

Lets just keep it to all CPUs for simplicty.
Also please add a comment that explains why we need that skew_tick on nohz_full.

Thanks!