Re: [RFC][PATCH] perf: Rewrite core context handling

[Song Liu]

Hi Peter,

> On Oct 10, 2018, at 3:45 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> Hi all,
> 
> 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).
> 
> Notably:
> 
> - HW breakpoint PMU
> - ARM big.little PMU
> - Intel Branch Monitoring PMU
> 
> 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.
> 
> Something a little like:
> 
>              ,------------------------[1:n]---------------------.
>              V                                                  V
>    perf_event_context <-[1:n]-> perf_event_pmu_context <--- perf_event
>              ^                      ^     |                     |
>              `--------[1:n]---------'     `-[n:1]-> pmu <-[1:n]-'
> 
> This patch builds (provided you disable CGROUP_PERF), boots and survives
> perf-top without the machine catching fire.
> 
> There's still a fair bit of loose ends (look for XXX), but I think this
> is the direction we should be going.
> 
> Comments?

This might be a little off topic...

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

Thanks,
Song