From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756375Ab0CKJ4U (ORCPT ); Thu, 11 Mar 2010 04:56:20 -0500 Received: from mail.gmx.net ([213.165.64.20]:47515 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755285Ab0CKJ4S (ORCPT ); Thu, 11 Mar 2010 04:56:18 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/50gF4H6v5KrPlVbQk5nIBOxjgXPT+nQX5TUGfyb 8ukjqhyx/TzNRE Subject: Re: [patch 6/12] sched: fix select_idle_sibling() 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 10:56:09 +0100 Message-Id: <1268301369.6785.36.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: 0.45000000000000001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sched: fix select_idle_sibling() Don't bother with selection when the current cpu is idle. Recent load balancing changes also make it no longer necessary to check wake_affine() success before returning the selected sibling, so we now always use it. Signed-off-by: Mike Galbraith Cc: Ingo Molnar Cc: Peter Zijlstra LKML-Reference: --- kernel/sched_fair.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -1438,7 +1438,7 @@ static int select_task_rq_fair(struct ta int cpu = smp_processor_id(); int prev_cpu = task_cpu(p); int new_cpu = cpu; - int want_affine = 0; + int want_affine = 0, cpu_idle = !current->pid; int want_sd = 1; int sync = wake_flags & WF_SYNC; @@ -1496,13 +1496,15 @@ static int select_task_rq_fair(struct ta * If there's an idle sibling in this domain, make that * the wake_affine target instead of the current cpu. */ - if (tmp->flags & SD_SHARE_PKG_RESOURCES) + if (!cpu_idle && tmp->flags & SD_SHARE_PKG_RESOURCES) target = select_idle_sibling(p, tmp, target); if (target >= 0) { if (tmp->flags & SD_WAKE_AFFINE) { affine_sd = tmp; want_affine = 0; + if (target != cpu) + cpu_idle = 1; } cpu = target; } @@ -1518,6 +1520,7 @@ static int select_task_rq_fair(struct ta sd = tmp; } +#ifdef CONFIG_FAIR_GROUP_SCHED if (sched_feat(LB_SHARES_UPDATE)) { /* * Pick the largest domain to update shares over @@ -1531,9 +1534,12 @@ static int select_task_rq_fair(struct ta if (tmp) update_shares(tmp); } +#endif - if (affine_sd && wake_affine(affine_sd, p, sync)) - return cpu; + if (affine_sd) { + if (cpu_idle || cpu == prev_cpu || wake_affine(affine_sd, p, sync)) + return cpu; + } while (sd) { int load_idx = sd->forkexec_idx;