Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755158AbYK0M1t (ORCPT ); Thu, 27 Nov 2008 07:27:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752659AbYK0M1l (ORCPT ); Thu, 27 Nov 2008 07:27:41 -0500 Received: from one.firstfloor.org ([213.235.205.2]:46785 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751677AbYK0M1k (ORCPT ); Thu, 27 Nov 2008 07:27:40 -0500 Date: Thu, 27 Nov 2008 13:38:11 +0100 From: Andi Kleen To: Thomas Gleixner Cc: David Miller , eranian@gmail.com, eranian@googlemail.com, andi@firstfloor.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mingo@elte.hu, x86@kernel.org, sfr@canb.auug.org.au Subject: Re: [patch 05/24] perfmon: X86 generic code (x86) Message-ID: <20081127123811.GJ6703@one.firstfloor.org> References: <7c86c4470811270209q18d4e83aq8901837159838cc4@mail.gmail.com> <20081127113115.GH6703@one.firstfloor.org> <7c86c4470811270335p2dbd61ebpe2c584e32d8b2292@mail.gmail.com> <20081127.034247.72331360.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1406 Lines: 35 On Thu, Nov 27, 2008 at 12:49:37PM +0100, Thomas Gleixner wrote: > On Thu, 27 Nov 2008, David Miller wrote: > > > From: "stephane eranian" > > Date: Thu, 27 Nov 2008 12:35:54 +0100 > > > > > I am still wondering how Oprofile handles the case where multiple > > > processes or threads access the same file descriptor. > > > > There's only one profiling buffer active on a given cpu, > > so it's pure per-cpu value insertion. > > > > In any event I think that NMI profiling is a must, especially > > for the kernel. You get total unusable crap otherwise. I > > just learned this the hard way having gotten an NMI'ish scheme > > working on sparc64 just the other day. > > Not arguing about that, I'm just not agreeing with the implementation. > > So for the moment we can go w/o the NMI and implement it cleanly after > we got the initial lot in. Note once Stephane readds PEBS support (it is currently stripped out) you'll be also able to get somewhat reasonable results at least on modern Intel x86 without NMI profiling. But longer term it is still very useful because PEBS has some drawbacks too -Andi -- ak@linux.intel.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/