linux-kernel - Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too

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Message-ID: <YheK2oesh/cxvi6j@fuller.cnet>
Date:   Thu, 24 Feb 2022 10:40:42 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Aaron Tomlin <atomlin@...hat.com>
Cc:     Aaron Tomlin <atomlin@...mlin.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Christoph Lameter <cl@...ux.com>, tglx@...utronix.de,
        mingo@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Phil Auld <pauld@...hat.com>
Subject: Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the
 idle tick was stopped too

On Thu, Feb 24, 2022 at 01:28:16PM +0000, Aaron Tomlin wrote:
> On Thu 2022-02-24 10:14 -0300, Marcelo Tosatti wrote:
> > If the per-CPU vmstat_update is limited to happen once per second, that
> > shouldnt be a significant performance impact?
> 
> Perhaps not. Albeit, is the interrupt worth it? 

Its a requirement for correctness right?

> Then again it could indeed
> be a long time before the idle task is selected and a return to idle code
> were we'd check for any remaining differentials with the aforementioned
> patch.

Or a long time before userspace returns to kernel.