From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755901Ab0EFImQ (ORCPT ); Thu, 6 May 2010 04:42:16 -0400 Received: from hera.kernel.org ([140.211.167.34]:37462 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751191Ab0EFImO (ORCPT ); Thu, 6 May 2010 04:42:14 -0400 Message-ID: <4BE280AA.6020304@kernel.org> Date: Thu, 06 May 2010 10:41:14 +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: Ingo Molnar 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 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> <20100506082714.GA2036@elte.hu> In-Reply-To: <20100506082714.GA2036@elte.hu> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 06 May 2010 08:41:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Ingo. On 05/06/2010 10:27 AM, Ingo Molnar wrote: > 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. Okay. Well, cmwq's usage of it isn't that hairy. It's used for two things. 1. to count the number of currently running workers which I think is fine for such hooks. 2. to wake up another worker. I don't think this falls in the category of "behavior/semantics" change. It just does try_to_wake_up() with the only caveat being it's called under the rq lock so requires a different API. There's nothing which alters the scheduler behavior in any pervasive way. It just looks at the counter and wakes up another task if the condition is right *before* beginning any of real scheduling work. But, anyways, making a dedicated fixed function calls certainly isn't a problem and might as well be slightly cheaper as it's always gonna be there anyway. If that's preferred, I'll happily take that path. Thanks. -- tejun