From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932733AbZFOTEu (ORCPT ); Mon, 15 Jun 2009 15:04:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933740AbZFOTE3 (ORCPT ); Mon, 15 Jun 2009 15:04:29 -0400 Received: from tomts43-srv.bellnexxia.net ([209.226.175.110]:48237 "EHLO tomts43-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933426AbZFOTE2 (ORCPT ); Mon, 15 Jun 2009 15:04:28 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AokFAA43NkpMQWQl/2dsb2JhbACBT9U+hA0F Date: Mon, 15 Jun 2009 14:59:07 -0400 From: Mathieu Desnoyers To: Peter Zijlstra Cc: "H. Peter Anvin" , Linus Torvalds , Ingo Molnar , mingo@redhat.com, paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org, penberg@cs.helsinki.fi, vegard.nossum@gmail.com, efault@gmx.de, jeremy@goop.org, npiggin@suse.de, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods Message-ID: <20090615185907.GF6520@Krystal> References: <20090615171845.GA7664@elte.hu> <4A369508.2090707@zytor.com> <20090615184858.GD6520@Krystal> <1245091917.6741.185.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1245091917.6741.185.camel@laptop> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 14:57:04 up 107 days, 15:23, 3 users, load average: 0.27, 0.56, 0.81 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra (a.p.zijlstra@chello.nl) wrote: > On Mon, 2009-06-15 at 14:48 -0400, Mathieu Desnoyers wrote: > > we should not care that much about the performance hit of > > saving/restoring the cr2 register at each nmi entry/exit. > > But we do, perf counters very much cares about nmi performance. > To a point where it cannot afford a simple register save/restore ? There is "caring" and "_caring_". I am tempted to ask what NMI handler execution frequency you have in mind here to figure out if we are not trying to optimize sub-nanoseconds per minutes. ;) Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68