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

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To: Aaron Tomlin <atomlin@xxxxxxxxxx>
Subject: Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Date: Thu, 24 Feb 2022 10:40:42 -0300
Cc: Aaron Tomlin <atomlin@xxxxxxxxxxx>, Frederic Weisbecker <frederic@xxxxxxxxxx>, Christoph Lameter <cl@xxxxxxxxx>, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, Phil Auld <pauld@xxxxxxxxxx>
In-reply-to: <20220224132816.qsfa66ao3xdjdxxx@ava.usersys.com>
References: <20220203214339.1889971-1-atomlin@redhat.com> <20220217124729.GA743618@lothringen> <20220217142615.xqtiydixvnumyvei@ava.usersys.com> <20220217163205.GA748087@lothringen> <20220218125454.utlgmuhijklzr3if@ava.usersys.com> <20220219154616.pwsvh445x3vn7ltf@ava.usersys.com> <Yhd5olg9CjXSAf2s@fuller.cnet> <20220224130014.rmhtx3xlepybuxn2@ava.usersys.com> <YheE0joXm53Hxn4J@fuller.cnet> <20220224132816.qsfa66ao3xdjdxxx@ava.usersys.com>

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.

Follow-Ups:
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin

References:
- [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Frederic Weisbecker
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Frederic Weisbecker
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Marcelo Tosatti
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Marcelo Tosatti
- Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
  - From: Aaron Tomlin

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