Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756513AbYKUI3c (ORCPT ); Fri, 21 Nov 2008 03:29:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756036AbYKUI2p (ORCPT ); Fri, 21 Nov 2008 03:28:45 -0500 Received: from E23SMTP02.au.ibm.com ([202.81.18.163]:56284 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753134AbYKUI2o (ORCPT ); Fri, 21 Nov 2008 03:28:44 -0500 From: Vaidyanathan Srinivasan Subject: [RFC PATCH v4 3/7] sched: nominate preferred wakeup cpu To: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Peter Zijlstra Cc: Ingo Molnar , Dipankar Sarma , Balbir Singh , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Gregory Haskins , Vaidyanathan Srinivasan Date: Fri, 21 Nov 2008 14:01:14 +0530 Message-ID: <20081121083114.27075.2113.stgit@drishya.in.ibm.com> In-Reply-To: <20081121082533.27075.12056.stgit@drishya.in.ibm.com> References: <20081121082533.27075.12056.stgit@drishya.in.ibm.com> User-Agent: StGIT/0.14.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2247 Lines: 68 When the system utilisation is low and more cpus are idle, then the process waking up from sleep should prefer to wakeup an idle cpu from semi-idle cpu package (multi core package) rather than a completely idle cpu package which would waste power. Use the sched_mc balance logic in find_busiest_group() to nominate a preferred wakeup cpu. This info can be sored in appropriate sched_domain, but updating this info in all copies of sched_domain is not practical. Hence this information is stored in root_domain struct which is one copy per partitioned sched domain. The root_domain can be accessed from each cpu's runqueue and there is one copy per partitioned sched domain. Signed-off-by: Vaidyanathan Srinivasan --- kernel/sched.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 79b71f3..d28cd98 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -493,6 +493,17 @@ struct root_domain { #ifdef CONFIG_SMP struct cpupri cpupri; #endif +#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) + + /* + * Preferred wake up cpu nominated by sched_mc balance that will be + * used when most cpus are idle in the system indicating overall very + * low system utilisation. Triggered at POWERSAVINGS_BALANCE_WAKEUP(2) + */ + unsigned int sched_mc_preferred_wakeup_cpu; + +#endif + }; /* @@ -3090,6 +3101,7 @@ static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest, return 0; } + /* * find_busiest_group finds and returns the busiest CPU group within the * domain. It calculates and returns the amount of weighted load which @@ -3406,6 +3418,9 @@ out_balanced: if (this == group_leader && group_leader != group_min) { *imbalance = min_load_per_task; + if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) + cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu = + first_cpu(group_leader->cpumask); return group_min; } #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/