From: Andi Kleen <andi@firstfloor.org>
To: Stephane Eranian <eranian@google.com>
Cc: Andi Kleen <andi@firstfloor.org>, Jiri Olsa <jolsa@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Namhyung Kim <namhyung@kernel.org>,
Corey Ashford <cjashfor@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@elte.hu>, Paul Mackerras <paulus@samba.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH] perf x86: Change SandyBridge and IvyBrige instructions event to be precise
Date: Wed, 20 Feb 2013 22:48:16 +0100 [thread overview]
Message-ID: <20130220214816.GC2928@two.firstfloor.org> (raw)
In-Reply-To: <CABPqkBTCJF9eF_3Nj9nV=PNqVnrcZhkZ90oJfQ6tpHzFDFgptg@mail.gmail.com>
> I don't think it buys you much. People read too much into what
> PEBS gives you. I can show you examples where PEBS
> is worse than no PEBS.
Nothing is perfect in sampling, but the precise instructions event
is definitely better in a range of situations. It avoids
a lot of shadow effects.
I think it's a good choice for a lot of situations, although
on Ivy Bridge without EventingRip the BB walking is still
fairly expensive.
It would be a good default for the "user only asks for instructions
for sampling and nothing else" situation, especially on Haswell
which has EventingRip. But that's not straight forward to detect.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2013-02-20 21:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-20 20:39 Jiri Olsa
2013-02-20 20:55 ` Andi Kleen
2013-02-20 21:01 ` Stephane Eranian
2013-02-20 21:29 ` Jiri Olsa
2013-02-20 21:48 ` Andi Kleen [this message]
2013-02-20 21:18 ` Jiri Olsa
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