linux-kernel - Re: [PATCH v3] perf: Store active software events in a hashlist

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Message-ID: <1271415214.4807.1957.camel@twins>
Date:	Fri, 16 Apr 2010 12:53:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v3] perf: Store active software events in a hashlist

On Wed, 2010-04-14 at 02:53 +0200, Frederic Weisbecker wrote:
> 
> Each time a software event triggers, we need to walk through
> the entire list of events from the current cpu and task contexts
> to retrieve a running perf event that matches.
> We also need to check a matching perf event is actually counting.
> 
> This walk is wasteful and makes the event fast path scaling
> down with a growing number of events running on the same
> contexts.
> 
> To solve this, we store the running perf events in a hashlist to
> get an immediate access to them against their type:event_id when
> they trigger. 

Looks good, thanks Frederic!
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