Re: [PATCH v1 5/6] mm: make vmstat_update periodic run conditional

[KOSAKI Motohiro]

> > @@ -1204,8 +1265,14 @@ static int __init setup_vmstat(void)
> >
> >   	register_cpu_notifier(&vmstat_notifier);
> >
> > +	INIT_DELAYED_WORK_DEFERRABLE(&vmstat_monitor_work,
> > +				vmstat_update_monitor);
> > +	queue_delayed_work(system_unbound_wq,
> > +				&vmstat_monitor_work,
> > +				round_jiffies_relative(HZ));
> > +
> >   	for_each_online_cpu(cpu)
> > -		start_cpu_timer(cpu);
> > +		setup_cpu_timer(cpu);
> >   #endif
> >   #ifdef CONFIG_PROC_FS
> >   	proc_create("buddyinfo", S_IRUGO, NULL,&fragmentation_file_operations);
>
> So the monitoring thread just bounces around the system? Hope that the
> scheduler does the right thing to keep it on processors that do some other
> work.

Good point. Usually, all cpus have update items and monitor worker only makes
new noise. I think this feature is only useful some hpc case.  So I wonder if
this vmstat improvemnt can integrate Frederic's Nohz cpusets activity. I.e.
vmstat-update integrate timer house keeping and automatically stop when stopping
hz house keeping.

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