Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755887AbYK0MbZ (ORCPT ); Thu, 27 Nov 2008 07:31:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753210AbYK0MbM (ORCPT ); Thu, 27 Nov 2008 07:31:12 -0500 Received: from fg-out-1718.google.com ([72.14.220.156]:51831 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753534AbYK0MbL (ORCPT ); Thu, 27 Nov 2008 07:31:11 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:reply-to:to:subject:cc:in-reply-to :mime-version:content-type:content-transfer-encoding :content-disposition:references; b=iTtuoRvIIxaP+3dzNDWBNLPT3iBwDw0ezsY0aihuMBDqAuZ/qy4zpIu2mFv/rMLhDF lkERfBq5Ky0Dq03i3mTNamA0+VxcPyhU1dNsOkxWUHAFN/wkl8UlrU55AilR5giH7YAw FikLOam+p9SJ7X5d4D0S6EJyG5aA4JYO3AldA= Message-ID: <7c86c4470811270431n5cf1b863tc4f8c7829283e332@mail.gmail.com> Date: Thu, 27 Nov 2008 13:31:08 +0100 From: "stephane eranian" Reply-To: eranian@gmail.com To: "Andi Kleen" Subject: Re: [patch 05/24] perfmon: X86 generic code (x86) Cc: "Thomas Gleixner" , "David Miller" , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mingo@elte.hu, x86@kernel.org, sfr@canb.auug.org.au In-Reply-To: <20081127123811.GJ6703@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <7c86c4470811270209q18d4e83aq8901837159838cc4@mail.gmail.com> <20081127113115.GH6703@one.firstfloor.org> <7c86c4470811270335p2dbd61ebpe2c584e32d8b2292@mail.gmail.com> <20081127.034247.72331360.davem@davemloft.net> <20081127123811.GJ6703@one.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1582 Lines: 36 On Thu, Nov 27, 2008 at 1:38 PM, Andi Kleen wrote: > 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 That's true for Intel. On AMD64, I think you can get at most one sample out of a irq-off region using IBS. -- 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/