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From: Andi Kleen <andi@firstfloor.org>
To: eranian@gmail.com
Cc: Andi Kleen <andi@firstfloor.org>,
	Eric Dumazet <dada1@cosmosbay.com>,
	Mikael Pettersson <mikpe@it.uu.se>,
	Robert Richter <robert.richter@amd.com>,
	oprofile-list@lists.sf.net, Ingo Molnar <mingo@elte.hu>,
	Jiri Kosina <jkosina@suse.cz>, Jiri Benc <jbenc@suse.cz>,
	Vilem Marsik <vmarsik@suse.cz>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
	linux-kernel@vger.kernel.org
Subject: Re: Oprofile : need to adjust PC by 16 bytes
Date: Mon, 17 Nov 2008 16:24:34 +0100	[thread overview]
Message-ID: <20081117152434.GM6703@one.firstfloor.org> (raw)
In-Reply-To: <7c86c4470811170702y127c9249m9b86b65a38a3e05c@mail.gmail.com>

On Mon, Nov 17, 2008 at 04:02:19PM +0100, stephane eranian wrote:

Thanks for explaining it better than I could.

Just a minor correction.

> But it can be very large when overflow happens
> during a kernel critical section
> where interrupts are off.

Actually oprofile uses the NMI to avoid that particular problem.
It still has limits, e.g. no profiling of SMM sections.

> There is nothing SW can do about all of this.

Yes profiling on a out of order machine is hard.

> Furthermore, PEBS can record samples while
> in kernel critical sections. 

Again with oprofile that works too without PEBS.

-Andi

  parent reply	other threads:[~2008-11-17 15:15 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-13 20:57 Oprofile [still] doesn't work on 2.6.28-rc4 on certain CPU Jiri Kosina
2008-11-13 21:24 ` Ingo Molnar
2008-11-13 21:27   ` Jiri Kosina
2008-11-13 21:37     ` Ingo Molnar
2008-11-13 21:49       ` Eric Dumazet
2008-11-14 15:25         ` Oprofile : need to adjust PC by 16 bytes Eric Dumazet
2008-11-14 15:59           ` Andi Kleen
2008-11-14 16:02             ` Eric Dumazet
2008-11-14 17:01           ` Mikael Pettersson
2008-11-14 17:21             ` Eric Dumazet
2008-11-14 17:50               ` Andi Kleen
2008-11-15 16:30                 ` Eric Dumazet
2008-11-15 18:36                   ` Andi Kleen
2008-11-17 15:02                     ` stephane eranian
2008-11-17 15:16                       ` Eric Dumazet
2008-11-17 15:24                       ` Andi Kleen [this message]
2008-11-14 10:09     ` Oprofile [still] doesn't work on 2.6.28-rc4 on certain CPU Robert Richter
2008-11-14 11:12       ` Jiri Kosina
2008-11-13 21:33   ` Maynard Johnson

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