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Date:   Mon, 25 Apr 2022 15:27:00 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Christoph Lameter <cl@gentwo.de>
Cc:     Aaron Tomlin <atomlin@redhat.com>, frederic@kernel.org,
        mtosatti@redhat.com, tglx@linutronix.de, mingo@kernel.org,
        pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH v3] tick/sched: Ensure quiet_vmstat() is called when
 the idle tick was stopped too
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On Mon, Apr 25, 2022 at 02:09:06PM +0200, Christoph Lameter wrote:
> On Mon, 25 Apr 2022, Aaron Tomlin wrote:
> 
> > Yes, in the context of nohz, this patch should ensure it, if required, when
> > the idle tick is to be stopped.
> 
> What I said was that it is generally useful. Even in the non NOHZ case.
> 
> Folding the vmstat diffs *always* when entering idle prevents unnecessary
> wakeups and processing in the future and also provides more accurate
> counters for the VM allowing better decision to be made on reclaim.

I'm thinking you're going to find a ton of regressions if you try it
though; some workloads go idle *very* shortly, doing all this accounting
is going to be counter-productive.