linux-kernel - Re: [PATCH] perf: Don't schedule tracepoints when exclude

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Message-ID: <20110409132709.GA1799@nowhere>
Date:	Sat, 9 Apr 2011 15:27:14 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf: Don't schedule tracepoints when exclude_kernel
 is set

On Sat, Apr 09, 2011 at 03:14:44PM +0200, Peter Zijlstra wrote:
> On Fri, 2011-04-08 at 22:57 +0200, Frederic Weisbecker wrote:
> > Instead of checking attr.exclude_kernel anytime a tracepoint
> > event triggers, simply don't schedule the tracepoint it that
> > attribute is set. This makes one test less in the tracing
> > path.
> 
> Meh, I'd much rather someone spend some time on finishing the below,
> which is a much bigger improvement for trace-events.

I secretely added that to my pile already :)
That's indeed something we really want.

The above is just a little thing I noticed yesterday and I wanted
to fix. Nothing more.

About that tracepoint collection, I'm not sure I like the idr though.
That thing seems to be O(log(n)), I which we can rather approach O(1)
when possible, using a hlist perhaps.
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