Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752506AbYLRSMa (ORCPT ); Thu, 18 Dec 2008 13:12:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751946AbYLRSMU (ORCPT ); Thu, 18 Dec 2008 13:12:20 -0500 Received: from e28smtp09.in.ibm.com ([59.145.155.9]:34414 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751729AbYLRSMS (ORCPT ); Thu, 18 Dec 2008 13:12:18 -0500 Date: Thu, 18 Dec 2008 23:42:10 +0530 From: Balbir Singh To: Vaidyanathan Srinivasan Cc: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Peter Zijlstra , Ingo Molnar , Dipankar Sarma , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Gregory Haskins , Pavel Machek , Andrew Morton Subject: Re: [PATCH v7 4/8] sched: nominate preferred wakeup cpu Message-ID: <20081218181210.GG26572@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com Mail-Followup-To: Vaidyanathan Srinivasan , Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Peter Zijlstra , Ingo Molnar , Dipankar Sarma , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Gregory Haskins , Pavel Machek , Andrew Morton References: <20081218175313.29812.4781.stgit@drishya.in.ibm.com> <20081218175622.29812.69201.stgit@drishya.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20081218175622.29812.69201.stgit@drishya.in.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Vaidyanathan Srinivasan [2008-12-18 23:26:22]: > 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 | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 0b9bbbd..3415fa3 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -493,6 +493,14 @@ 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 > }; > > /* > @@ -3407,6 +3415,10 @@ 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 Acked-by: Balbir Singh -- Balbir -- 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/