Re: [PATCH 1/2] perf: Add munmap callback

[Liang, Kan]

On 10/24/2018 12:32 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Oct 24, 2018 at 09:23:34AM -0700, Andi Kleen escreveu:
> > > +void perf_event_munmap(void)
> > > +{
> > > +	struct perf_cpu_context *cpuctx;
> > > +	unsigned long flags;
> > > +	struct pmu *pmu;
> > > +
> > > +	local_irq_save(flags);
> > > +	list_for_each_entry(cpuctx, this_cpu_ptr(&sched_cb_list), sched_cb_entry) {
> >
> > Would be good have a fast path here that checks for the list being empty
> > without disabling the interrupts. munmap can be somewhat hot. I think
> > it's ok to make it slower with perf running, but we shouldn't impact
> > it without perf.
>
> Right, look at how its counterpart, perf_event_mmap() works:
>
> void perf_event_mmap(struct vm_area_struct *vma)
> {
>          struct perf_mmap_event mmap_event;
>
>          if (!atomic_read(&nr_mmap_events))
>                  return;
> <SNIP>
> }

Thanks. I'll add the nr_mmap_events check in V2.

Thanks,
Kan