From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934734Ab0EENKO (ORCPT ); Wed, 5 May 2010 09:10:14 -0400 Received: from hera.kernel.org ([140.211.167.34]:53165 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755113Ab0EENKL (ORCPT ); Wed, 5 May 2010 09:10:11 -0400 Message-ID: <4BE16DFA.3070204@kernel.org> Date: Wed, 05 May 2010 15:09:14 +0200 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: Avi Kivity CC: Peter Zijlstra , mingo@elte.hu, efault@gmx.de, paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCHSET] sched,perf: unify tracers in sched and move perf on top of TP References: <1272976724-14312-1-git-send-email-tj@kernel.org> <1272994165.1642.203.camel@laptop> <4BE0FB68.7080403@kernel.org> <1273050400.1642.229.camel@laptop> <4BE13B33.3030709@kernel.org> <1273053073.1642.235.camel@laptop> <4BE1406C.2000400@kernel.org> <1273059488.1642.245.camel@laptop> <4BE165B0.1070300@redhat.com> In-Reply-To: <4BE165B0.1070300@redhat.com> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Wed, 05 May 2010 13:09:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 05/05/2010 02:33 PM, Avi Kivity wrote: > On 05/05/2010 02:38 PM, Peter Zijlstra wrote: >> As it stands I'd argue to simply drop this whole idea. The SCHED_EVENT() >> thing doesn't look like its worth the obfuscation and I'm very much >> opposed to making perf and sched_notifiers rely on tracepoints. > > We can make perf rely on sched_notifiers, I think it's exactly the same > case as kvm - extra cpu state that needs switching at context switch > time. We could also make fpu switching use sched_notifiers, but that's > pushing it a bit. Oh, that was my first attempt too. The difference between TPs and sched_notifiers is the enable condition. TP is system-wide while sched_notifier is per-task. The thing is that for perf hooks, system-wide enable condition works much better. Also, w/ sched_notifiers, there's the problem that no one else but self can enable/disable it (which can be changed but doing it without causing call time overhead requires a bit of effort). Thanks. -- tejun