From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755558Ab0EFI1s (ORCPT ); Thu, 6 May 2010 04:27:48 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:51395 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755275Ab0EFI1p (ORCPT ); Thu, 6 May 2010 04:27:45 -0400 Date: Thu, 6 May 2010 10:27:14 +0200 From: Ingo Molnar To: Tejun Heo Cc: Frederic Weisbecker , Peter Zijlstra , efault@gmx.de, avi@redhat.com, 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 Message-ID: <20100506082714.GA2036@elte.hu> References: <1273053073.1642.235.camel@laptop> <4BE1406C.2000400@kernel.org> <1273059488.1642.245.camel@laptop> <4BE1648B.1080709@kernel.org> <20100505165532.GC14323@elte.hu> <1273083173.1642.250.camel@laptop> <1273083396.1642.251.camel@laptop> <20100505183000.GF6320@nowhere> <20100506062855.GD1172@elte.hu> <4BE26B96.4040007@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BE26B96.4040007@kernel.org> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Tejun Heo wrote: > Hello, > > On 05/06/2010 08:28 AM, Ingo Molnar wrote: > > ( They are also under intense optimization - the jump-tracepoints patch makes > > them probably even cheaper than preempt notifiers, in the off case. ) > > I mostly agree on other points but TPs and sched_notifiers are inherently > different in how they are enabled/disabled. sched_notifiers are > enabled/disabled per-task and at least w/ cmwq, there will always be some > tasks with active sched_notifiers so code level optimizations aren't really > useful. Note that preempt notifiers used to modify scheduling behavior/semantics i'm really against. Please get that functionality into the scheduler - especially if it's essentially always-on. Preempt notifiers are for things like KVM which want to do extended context saving. They are _NOT_ 'hooks' into the scheduler. Ingo