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

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Date:   Wed, 24 Oct 2018 09:23:34 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
        acme@...nel.org, linux-kernel@...r.kernel.org, bp@...en8.de,
        eranian@...gle.com
Subject: Re: [PATCH 1/2] perf: Add munmap callback

> +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.

-Andi