Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761426AbXKMVvX (ORCPT ); Tue, 13 Nov 2007 16:51:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759024AbXKMVvD (ORCPT ); Tue, 13 Nov 2007 16:51:03 -0500 Received: from one.firstfloor.org ([213.235.205.2]:54609 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758060AbXKMVvA (ORCPT ); Tue, 13 Nov 2007 16:51:00 -0500 Date: Tue, 13 Nov 2007 22:50:56 +0100 From: Andi Kleen To: Stephane Eranian Cc: Andi Kleen , akpm@osdl.org, Robert Richter , gregkh@suse.de, linux-kernel@vger.kernel.org, perfmon@napali.hpl.hp.com, William Cohen , perfmon2-devel@lists.sourceforge.net Subject: Re: [perfmon] Re: [perfmon2] perfmon2 merge news Message-ID: <20071113215056.GB17593@one.firstfloor.org> References: <20071109120627.60ec9ab4.akpm@linux-foundation.org> <20071109213829.GC28276@kroah.com> <20071113151718.GA3804@erda.amd.com> <4739C42F.8030208@redhat.com> <20071113175545.GD4319@frankl.hpl.hp.com> <4739EE13.2090006@redhat.com> <20071113211345.GB5747@frankl.hpl.hp.com> <20071113212902.GA17593@one.firstfloor.org> <20071113214628.GE5747@frankl.hpl.hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071113214628.GE5747@frankl.hpl.hp.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1018 Lines: 24 > Yes, horribly more complicated because of locking issues within perfmon. > As soon as you expose a file descriptor, you need some locking to prevent > multiple user threads (malicious or not) to compete to access the PMU state. Why do you need the file descriptor? One of the main problems with perfmon is the complicated user interface. Naively I would assume just some thread global state should be sufficient. > I think the value add of NMI can be as well achieved with advanced PMU features > such as Intel Core 2 PEBS. True probably, although only on CPUs that support PEBS. Dropping features for old CPUs is unfortunately quite difficult in Linux, and in this case probably not an option because there are so many of them (e.g. all of AMD not Fam10h) -Andi - 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/