From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935382Ab3BTNcv (ORCPT ); Wed, 20 Feb 2013 08:32:51 -0500 Received: from merlin.infradead.org ([205.233.59.134]:49159 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935090Ab3BTNcu (ORCPT ); Wed, 20 Feb 2013 08:32:50 -0500 Message-ID: <1361367148.10155.30.camel@laptop> Subject: Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair() From: Peter Zijlstra To: Ingo Molnar Cc: Michael Wang , LKML , Paul Turner , Mike Galbraith , Andrew Morton , alex.shi@intel.com, Ram Pai , "Nikunj A. Dadhania" , Namhyung Kim Date: Wed, 20 Feb 2013 14:32:28 +0100 In-Reply-To: <20130220104958.GA9152@gmail.com> References: <51079178.3070002@linux.vnet.ibm.com> <20130220104958.GA9152@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.2-0ubuntu0.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2013-02-20 at 11:49 +0100, Ingo Molnar wrote: > The changes look clean and reasoable, I don't necessarily agree, note that O(n^2) storage requirement that Michael failed to highlight ;-) > any ideas exactly *why* it speeds up? That is indeed the most interesting part.. There's two parts to select_task_rq_fair(), the 'regular' affine wakeup path, and the fork/exec find_idlest_goo() path. At the very least we need to quantify which of these two parts contributes most to the speedup. In the power balancing discussion we already noted that the find_idlest_goo() is in need of attention.