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

[Peter Zijlstra]

On Tue, Oct 16, 2018 at 06:28:10PM +0000, Song Liu wrote:
> > How about this: 
> > 
> > 1. Keep multiple perf_cpu_context per CPU, just like before this patch. 
> > 
> > 2. For perf_event_context, add PMU as an order for the RB tree. 
> > 
> > 3. (hw) pmu->perf_cpu_context->ctx only has events for this PMU (and sw 
> >   events moved to this context).
> > 
> > 4. task->perf_event_ctxp has events for all PMUs. 
> > 
> > With this path, we keep the existing perf_cpu_context/perf_event_context
> > logic as-is, which I think is simpler than the new logic (with extra
> > *_pmu_context). And it should also solve the problem. 
> > 
> > Does this make sense? If this doesn't look too broken, I am happy to
> > draft RFC for it. 
> > 
> 
> I am not sure whether you missed this one, or found it totally insane. 
> Could you please share your comments on it? My gut feeling is that this 
> would be a simpler patch to solve the problem (two hw PMUs). (It might 
> be less efficient though). 

Ah, sorry, somehow this email got lost.

That makes task and cpu contexts wildly different, which will complicate
matters I feel.