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

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