From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757611Ab1GASm3 (ORCPT ); Fri, 1 Jul 2011 14:42:29 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:32815 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753986Ab1GASm2 (ORCPT ); Fri, 1 Jul 2011 14:42:28 -0400 Subject: [PATCH] sched: Check nr_running before calling pick_next_task in schedule(). From: Rakib Mullick To: Ingo Molnar Cc: Peter Zijlstra , linux-kernel Content-Type: text/plain; charset="UTF-8" Date: Sat, 02 Jul 2011 00:41:51 +0600 Message-ID: <1309545711.4303.2.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 (2.32.1-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently at schedule(), when we call pick_next_task we don't check whether current rq is empty or not. Since idle_balance can fail, its nice to check whether we really have any task on rq or not. If not, we can call idle_sched_class.pick_next_task straight. Signed-off-by: Rakib Mullick --- diff --git a/kernel/sched.c b/kernel/sched.c index 5925275..a4f4f58 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4273,7 +4273,14 @@ need_resched: idle_balance(cpu, rq); put_prev_task(rq, prev); - next = pick_next_task(rq); + /* Since idle_balance can fail, its better to check rq->nr_running. + * Otherwise we can call idle_sched_class.pick_next_task straight, + * cause we need to do some accounting. + */ + if (likely(rq->nr_running)) + next = pick_next_task(rq); + else + next = idle_sched_class.pick_next_task(rq); clear_tsk_need_resched(prev); rq->skip_clock_update = 0;