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

[Peter Zijlstra <peterz@infradead.org>]

On Thu, 2010-01-21 at 11:21 +0100, Stephane Eranian wrote:

> Are you suggesting a speculative approach where you first try simply
> accumulate then schedule and if this fails, then restart the whole
> loop but this time adding and scheduling each event individually?
> For groups, you'd have to fail the group if one of its events fails.

No, I'm only talking about groups. The complaint from frederic was that
current hw_perf_group_sched_in() implementations have to basically
replicate all of the group_sched_in() and event_sched_in() stuff, which
seems wasteful.

So I was thinking of an alternative interface that would give the same
end result but not as much code replication.

I'm now leaning towards adding a parameter to ->enable() to postpone
schedulability and add a hw_perf_validate() like call.

With that I'm also looking at what would be the sanest way to multiplex
all the current weak hw_perf* functions in the light of multiple pmu
implementations.