Re: [PATCH] mm/vmstat: spread vmstat_update requeue across the stat interval

[Breno Leitao]

On Wed, Apr 01, 2026 at 04:50:03PM +0100, Usama Arif wrote:
> >>
> >> This is awesome! Maybe this needs to be done to vmstat_shepherd() as well?
> >>
> >> vmstat_shepherd() still queues work with delay 0 on all CPUs that
> >> need_update() in its for_each_online_cpu() loop:
> >>
> >>       if (!delayed_work_pending(dw) && need_update(cpu))
> >>           queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
> >>
> >> So when the shepherd fires, it kicks all dormant CPUs' vmstat workers
> >> simultaneously.
> >>
> >> Under sustained memory pressure on a large system, I think the shepherd
> >> fires every sysctl_stat_interval and could re-trigger the same lock
> >> contention?
> > 
> > Good point - incorporating similar spreading logic in vmstat_shepherd()
> > would indeed address the simultaneous queueing issue you've described.
> > 
> > Should I include this in a v2 of this patch, or would you prefer it as
> > a separate follow-up patch?
> 
> I think it can be a separate follow-up patch, but no strong preference.

Thanks!

I will send a follow-up patch soon.
--breno