From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756576Ab0CKKBZ (ORCPT ); Thu, 11 Mar 2010 05:01:25 -0500 Received: from mail.gmx.net ([213.165.64.20]:36462 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755457Ab0CKKBX (ORCPT ); Thu, 11 Mar 2010 05:01:23 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/HuEBMxH7HQKDR/zcq2p+x6idaAc9WIUo/d7PoLg oD8VakQuCggZ8M Subject: Re: [patch 11/12] sched: remove ASYM_GRAN feature From: Mike Galbraith To: Peter Zijlstra Cc: Ingo Molnar , LKML In-Reply-To: <1268300950.6785.27.camel@marge.simson.net> References: <1268300950.6785.27.camel@marge.simson.net> Content-Type: text/plain Date: Thu, 11 Mar 2010 11:01:15 +0100 Message-Id: <1268301675.6785.44.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 X-FuHaFi: 0.46999999999999997 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sched: remove ASYM_GRAN feature This features has been enabled for quite a while, after testing showed that easing preemption for light tasks was harmful to high priority threads. Remove it. Signed-off-by: Mike Galbraith Cc: Ingo Molnar Cc: Peter Zijlstra LKML-Reference: --- kernel/sched_fair.c | 28 +++++++++++----------------- kernel/sched_features.h | 6 ------ 2 files changed, 11 insertions(+), 23 deletions(-) Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -1582,24 +1582,18 @@ wakeup_gran(struct sched_entity *curr, s /* * Since its curr running now, convert the gran from real-time * to virtual-time in his units. + * + * By using 'se' instead of 'curr' we penalize light tasks, so + * they get preempted easier. That is, if 'se' < 'curr' then + * the resulting gran will be larger, therefore penalizing the + * lighter, if otoh 'se' > 'curr' then the resulting gran will + * be smaller, again penalizing the lighter task. + * + * This is especially important for buddies when the leftmost + * task is higher priority than the buddy. */ - if (sched_feat(ASYM_GRAN)) { - /* - * By using 'se' instead of 'curr' we penalize light tasks, so - * they get preempted easier. That is, if 'se' < 'curr' then - * the resulting gran will be larger, therefore penalizing the - * lighter, if otoh 'se' > 'curr' then the resulting gran will - * be smaller, again penalizing the lighter task. - * - * This is especially important for buddies when the leftmost - * task is higher priority than the buddy. - */ - if (unlikely(se->load.weight != NICE_0_LOAD)) - gran = calc_delta_fair(gran, se); - } else { - if (unlikely(curr->load.weight != NICE_0_LOAD)) - gran = calc_delta_fair(gran, curr); - } + if (unlikely(se->load.weight != NICE_0_LOAD)) + gran = calc_delta_fair(gran, se); return gran; } Index: linux-2.6/kernel/sched_features.h =================================================================== --- linux-2.6.orig/kernel/sched_features.h +++ linux-2.6/kernel/sched_features.h @@ -17,12 +17,6 @@ SCHED_FEAT(START_DEBIT, 1) SCHED_FEAT(WAKEUP_PREEMPT, 1) /* - * When converting the wakeup granularity to virtual time, do it such - * that heavier tasks preempting a lighter task have an edge. - */ -SCHED_FEAT(ASYM_GRAN, 1) - -/* * Use the SYNC wakeup hint, pipes and the likes use this to indicate * the remote end is likely to consume the data we just wrote, and * therefore has cache benefit from being placed on the same cpu, see