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From:   Song Liu <songliubraving@fb.com>
To:     Peter Zijlstra <peterz@infradead.org>
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Subject: Re: [RFC][PATCH] perf: Rewrite core context handling
Thread-Topic: [RFC][PATCH] perf: Rewrite core context handling
Thread-Index: AQHUYIaFJ/VvvMmSxkC06uIJGGK3pKUsbfoA
Date:   Tue, 23 Oct 2018 06:13:29 +0000
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Hi Peter,

> On Oct 10, 2018, at 3:45 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>=20
> Hi all,
>=20
> There have been various issues and limitations with the way perf uses
> (task) contexts to track events. Most notable is the single hardware PMU
> task context, which has resulted in a number of yucky things (both
> proposed and merged).
>=20
> Notably:
>=20
> - HW breakpoint PMU
> - ARM big.little PMU
> - Intel Branch Monitoring PMU
>=20
> Since we now track the events in RB trees, we can 'simply' add a pmu
> order to them and have them grouped that way, reducing to a single
> context. Of course, reality never quite works out that simple, and below
> ends up adding an intermediate data structure to bridge the context ->
> pmu mapping.
>=20
> Something a little like:
>=20
>              ,------------------------[1:n]---------------------.
>              V                                                  V
>    perf_event_context <-[1:n]-> perf_event_pmu_context <--- perf_event
>              ^                      ^     |                     |
>              `--------[1:n]---------'     `-[n:1]-> pmu <-[1:n]-'
>=20
> This patch builds (provided you disable CGROUP_PERF), boots and survives
> perf-top without the machine catching fire.
>=20
> There's still a fair bit of loose ends (look for XXX), but I think this
> is the direction we should be going.
>=20
> Comments?

This might be a little off topic...

What's you plan about this effort and the PMU sharing work=20
(https://lkml.org/lkml/2018/10/4/10)? Would PMU sharing work better/simpler
with this effort?=20

Thanks,
Song