From: Andi Kleen <andi@firstfloor.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: eranian@gmail.com, Andi Kleen <andi@firstfloor.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-perf-users@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: Re: perf_event: rdpmc self-monitoring overhead issue
Date: Mon, 2 Sep 2013 19:26:59 +0200 [thread overview]
Message-ID: <20130902172659.GJ19750@two.firstfloor.org> (raw)
In-Reply-To: <alpine.DEB.2.10.1309020914030.26568@vincent-weaver-1.um.maine.edu>
> I assume he means MAP_POPULATE
Yes.
>
> which does improve things, from ~3000 cycles to ~219 cycles but that's
> still more overhead than the ~130 or so you get by manually touching the
> page first.
That seems odd. It should be the same.
Can you do a trace-cmd function trace and compare the two cases?
trace-cmd record -p function_graph ...
trace-cmd report
(as usual for tracing perf remove the useless -pg removal for perf in
kernel/events/Makefile and arch/x86/kernel/cpu/Makefile first)
-Andi
prev parent reply other threads:[~2013-09-02 17:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-30 17:55 perf_event: rdpmc self-monitoring overhead issue Vince Weaver
2013-08-30 18:05 ` Stephane Eranian
2013-08-30 18:35 ` Vince Weaver
2013-08-31 10:06 ` Mikael Pettersson
2013-09-02 2:50 ` Andi Kleen
2013-09-02 8:24 ` Stephane Eranian
2013-09-02 9:23 ` Andi Kleen
2013-09-02 13:15 ` Vince Weaver
2013-09-02 17:26 ` Andi Kleen [this message]
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