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Subject: Re: [PATCH v3] perf: Store active software events in a hashlist
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
       Eric Dumazet <eric.dumazet@gmail.com>
In-Reply-To: <1271206406-8575-1-git-send-regression-fweisbec@gmail.com>
References: <1271206406-8575-1-git-send-regression-fweisbec@gmail.com>
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Date: Fri, 16 Apr 2010 12:53:34 +0200
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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!