Re: [PATCH] perf_events: improve x86 event scheduling (v5)

[Peter Zijlstra <peterz@infradead.org>]

On Mon, 2010-01-18 at 15:20 +0100, Frederic Weisbecker wrote:
> 
> > Then there's still the question of having events of multiple hw pmus in
> > a single group, I'd be perfectly fine with saying that's not allowed,
> > what to others think?
> 
> 
> I guess we need that. It can be insteresting to couple
> hardware counters with memory accesses...or whatever.

That really depends on how easy it is to correlate events from the
various pmus. This case could indeed do that, but the core vs uncore
tihng is a lot less clear.

> Perf stat combines cache miss counting with page faults,
> cpu clock counters.

perf stat also doesn't use groups and it still works quite nicely.

> We shouldn't limit such possibilities for technical/cleanliness
> reasons. We should rather adapt.

Maybe, I'm not a very big fan of groups myself, but they are clearly
useful within a pmu, measuring cache misses through total-access for
example, but the use between pmus is questionable.

But sure, if we can do it without too much pain, that's fine.