linux-kernel - Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS

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Message-ID: <20171222075643.zrdsayvcpovysnre@hirez.programming.kicks-ass.net>
Date:   Fri, 22 Dec 2017 08:56:43 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Brendan Jackman <brendan.jackman@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS_KICK

On Thu, Dec 21, 2017 at 05:23:27PM +0100, Vincent Guittot wrote:
> Hi Peter,
> 
> I think that part of the proposal is missing.
> 
> One goal of the patchset was to kick an update of the stats of idle
> cpu when a task wake up on a cpu but the statistic has not been
> updated for a while.
> 
> That's why there where a call to nohz_kick_needed in the proposal to
> kick ilb but only for updating blocked load and not a full idle load
> balance
> 
> I can't find this call any more in your patchset

Yeah, I took it out because it didn't make sense to me. If you're waking
to a stale CPU, you're too late.