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Message-ID: <CAKfTPtDjVBP676kzW-5QF8nMyD1+WNnJWH4=gKPVV+55tm3Cng@mail.gmail.com> Date: Thu, 25 Feb 2021 09:05:11 +0100 From: Vincent Guittot <vincent.guittot@...aro.org> To: Valentin Schneider <valentin.schneider@....com> Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, linux-kernel <linux-kernel@...r.kernel.org>, Joel Fernandes <joel@...lfernandes.org>, Frederic Weisbecker <fweisbec@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Qais Yousef <qais.yousef@....com> Subject: Re: [PATCH 0/7 v4] move update blocked load outside newidle_balance Hi Valentin, On Wed, 24 Feb 2021 at 19:46, Valentin Schneider <valentin.schneider@....com> wrote: > > On 24/02/21 14:30, Vincent Guittot wrote: > > Joel reported long preempt and irq off sequence in newidle_balance because > > of a large number of CPU cgroups in use and having to be updated. This > > patchset moves the update outside newidle_imblance. This enables to early > > abort during the updates in case of pending irq as an example. > > > > Instead of kicking a normal ILB that will wakes up CPU which is already > > idle, patch 6 triggers the update of statistics in the idle thread of > > the CPU before selecting and entering an idle state. > > > > Changes on v4: > > - Add a dedicated bit for updating blocked load when entering idle. > > This simplifies the management of concurrency with kick_ilb. > > > > I believe that solves the issues vs nohz balance. > > One last thing for patch 7: mayhaps we could do a tad better to avoid > duplicate updates going through a heapful of leaf cfs rqs, see > > http://lore.kernel.org/r/jhj4kiht7oh.mognet@arm.com rq->last_blocked_load_update_tick is there only to filter duplicate update during _nohz_idle_balance but not for other normal LB. > > > Otherwise, feel free to add to the lot: > > Reviewed-by: Valentin Schneider <valentin.schneider@....com> >
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