Re: [RFC PATCH v3] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too

From: Peter Zijlstra
Date: Mon Apr 25 2022 - 09:28:05 EST

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.