linux-kernel - Re: [PATCH 4/5] sched/isolation: Residual 1Hz scheduler tick offload

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Message-ID: <CAFTL4hyd64a23Y0z7E2Cmay7Df795D52ouoh4T=uvtNnyBn=pA@mail.gmail.com>
Date:   Tue, 19 Dec 2017 17:32:17 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Christopher Lameter <cl@...ux.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Wanpeng Li <kernellwp@...il.com>,
        Mike Galbraith <efault@....de>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 4/5] sched/isolation: Residual 1Hz scheduler tick offload

2017-12-19 17:03 UTC+01:00, Christopher Lameter <cl@...ux.com>:
> On Tue, 19 Dec 2017, Frederic Weisbecker wrote:
>
>> Adding the boot parameter "isolcpus=nohz_offload" will now outsource
>> these scheduler ticks to the global workqueue so that a housekeeping CPU
>> handles that tick remotely.
>
> The vmstat processing required per cpu area access. How does that work if
> the code is running on a remote processor?

It seems that current::sched_class::task_tick() is ok with this, as it
uses per runqueues or per task datas. And both are passed as
arguments.