From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752229Ab3B1HXt (ORCPT ); Thu, 28 Feb 2013 02:23:49 -0500 Received: from mout.gmx.net ([212.227.17.22]:58003 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398Ab3B1HXs (ORCPT ); Thu, 28 Feb 2013 02:23:48 -0500 X-Greylist: delayed 302 seconds by postgrey-1.27 at vger.kernel.org; Thu, 28 Feb 2013 02:23:47 EST X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/UR/IqDoXUb0oYKXVfH7r3yhfcQejHxxW/BymUO2 /hpoKQX0SWLUCd Message-ID: <1362035917.4460.105.camel@marge.simpson.net> Subject: Re: [RFC PATCH] sched: wakeup buddy From: Mike Galbraith To: Michael Wang Cc: LKML , Ingo Molnar , Peter Zijlstra , Paul Turner , Alex Shi , Andrew Morton , Ram Pai , "Nikunj A. Dadhania" , Namhyung Kim Date: Thu, 28 Feb 2013 08:18:37 +0100 In-Reply-To: <512EFB4B.5040204@linux.vnet.ibm.com> References: <512EFB4B.5040204@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-02-28 at 14:38 +0800, Michael Wang wrote: > + /* > + * current is the only task on rq and it is > + * going to sleep, current cpu will be a nice > + * candidate for p to run on. > + */ The sync hint only means it might be going to sleep soon, and even then, there can still be enough execution overlap to be a win to schedule cross core. Sched pipe numbers will always be much prettier if you do wakeup cpu affine, as it's ~100% scheduler and ~100% sync. You may lose a lot on other stuff if you interpret the hint as gospel truth. IMHO, sched pipe is a "how fat have I become" benchmark, not "how well do I perform". The scheduler performs well when it makes more work happen. Playing ping-pong with yourself is _exercise_, not a job :) -Mike