Re: [patch v12 12/13] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean

Marcelo Tosatti
2022-05-03T21:02:31Z

On Wed, Apr 27, 2022 at 09:23:06AM +0200, Thomas Gleixner wrote:
> On Tue, Mar 15 2022 at 12:31, Marcelo Tosatti wrote:
> > /*
> > * The regular update, every sysctl_stat_interval, may come later
> > @@ -1948,9 +1977,19 @@ int vmstat_refresh(struct ctl_table *tab
> > * transiently negative values, report an error here if any of
> > * the stats is negative, so we know to go looking for imbalance.
> > */
> > - err = schedule_on_each_cpu(refresh_vm_stats);
> > - if (err)
> > - return err;
> > + cpus_read_lock();
> > + for_each_online_cpu(cpu) {
> > + struct work_struct *work = per_cpu_ptr(works, cpu);
> > +
> > + INIT_WORK(work, refresh_vm_stats);
> > + if (need_update(cpu) || need_drain_remote_zones(cpu))
>
> Of course that makes sense in general, but now you have two ways of
> deciding whether updating this is required.
>
> 1) The above
>
> 2) The per CPU boolean which tells whether vmstats are dirty or not.
>
> Can we have a third method perhaps?

Ok, will think of a third method to increase clarity :-)

By the fourth method it will be clear for sure!