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SubjectRe: [RFC][PATCH] perf: Rewrite core context handling
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> On Oct 16, 2018, at 11:10 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Oct 16, 2018 at 04:34:05PM +0000, Song Liu wrote:
>>>> 3. perf_event_pmu_context owns RB tree of events. Since we don't
>>>> need rotation across multiple hardware PMUs, the rotation is
>>>> within same perf_event_pmu_context.
>>>
>>> By keeping the RB trees in perf_event_context, we get bigger trees,
>>> which is more efficient (log(n+m) < log(n) + log(m))
>>>
>>> Also, specifically, it means we only need a single merge sort /
>>> iteration to schedule in a full context, instead of (again) doing 'n' of
>>> them.
>>>
>>> Also, given a context and a pmu, it is cheaper for finding the relevant
>>> events; this is needed for big.little for instance. Something the
>>> proposed patch doesn't fully flesh out.
>>
>> Would it be faster if we add a perf_event_pmu_context pointer to the
>> perf_event?
>
> + pmu_ctx = find_get_pmu_context(pmu, ctx, event);
> + if (IS_ERR(pmu_ctx)) {
> + err = PTR_ERR(pmu_ctx);
> + goto err_locked;
> + }
> + event->pmu_ctx = pmu_ctx;
>
> Like that?

Aha, we already have it. I misunderstood this one. Please ignore that.

Thanks,
Song

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