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

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Message-ID: <1264069717.4283.1148.camel@laptop>
Date:	Thu, 21 Jan 2010 11:28:37 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, perfmon2-devel@...ts.sf.net, eranian@...il.com
Subject: Re: [PATCH] perf_events: improve x86 event scheduling (v5)

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.

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