From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753876Ab2APJhL (ORCPT ); Mon, 16 Jan 2012 04:37:11 -0500 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:50877 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753694Ab2APJhJ (ORCPT ); Mon, 16 Jan 2012 04:37:09 -0500 Message-ID: <4F13EFBE.1030002@linux.vnet.ibm.com> Date: Mon, 16 Jan 2012 17:37:02 +0800 From: Michael Wang User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.24) Gecko/20111108 Thunderbird/3.1.16 MIME-Version: 1.0 To: Peter Zijlstra , ingo Molnar CC: LKML Subject: [PATCH] sched: Accelerate "pick_next_entity" under special condition Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12011600-3568-0000-0000-0000010FB57A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michael Wang We can avoid some useless operation in some special condition. For example: If we have "cfs_rq->next" and it can be use, we just return it directly. Signed-off-by: Michael Wang --- kernel/sched/fair.c | 28 +++++++++++++++++----------- 1 files changed, 17 insertions(+), 11 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 84adb2d..9fc2c3c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1295,6 +1295,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); +#define ENTITY_PREEMPT_ALLOWED(prev,next) (wakeup_preempt_entity(prev, next) < 1) + /* * Pick the next process, keeping these things in mind, in this order: * 1) keep things fair between processes/task groups @@ -1308,29 +1310,33 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) struct sched_entity *left = se; /* - * Avoid running the skip buddy, if running something else can - * be done without getting too unfair. + * Someone really wants this to run. If it's not unfair, run it. */ - if (cfs_rq->skip == se) { - struct sched_entity *second = __pick_next_entity(se); - if (second && wakeup_preempt_entity(second, left) < 1) - se = second; + if (cfs_rq->next && ENTITY_PREEMPT_ALLOWED(cfs_rq->next, left)) { + se = cfs_rq->next; + goto out; } /* * Prefer last buddy, try to return the CPU to a preempted task. */ - if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) + if (cfs_rq->last && ENTITY_PREEMPT_ALLOWED(cfs_rq->last, left)) { se = cfs_rq->last; + goto out; + } /* - * Someone really wants this to run. If it's not unfair, run it. + * Avoid running the skip buddy, if running something else can + * be done without getting too unfair. */ - if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) - se = cfs_rq->next; + if (cfs_rq->skip == se) { + struct sched_entity *second = __pick_next_entity(se); + if (second && ENTITY_PREEMPT_ALLOWED(second, left)) + se = second; + } +out: clear_buddies(cfs_rq, se); - return se; } -- 1.7.4.1