From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753219AbYLOGmd (ORCPT ); Mon, 15 Dec 2008 01:42:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751276AbYLOGmX (ORCPT ); Mon, 15 Dec 2008 01:42:23 -0500 Received: from E23SMTP05.au.ibm.com ([202.81.18.174]:34956 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257AbYLOGmW (ORCPT ); Mon, 15 Dec 2008 01:42:22 -0500 Date: Mon, 15 Dec 2008 12:10:56 +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 Subject: Re: [RFC PATCH v5 3/7] sched: nominate preferred wakeup cpu Message-ID: <20081215064056.GD18403@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 References: <20081211173831.2020.57550.stgit@drishya.in.ibm.com> <20081211174257.2020.53943.stgit@drishya.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20081211174257.2020.53943.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 [2008-12-11 23:12:57]: > 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 6bea99b..0918677 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) Is the root domain good enough? What is POWERSAVINGS_BALANCE_WAKEUP(2), is it sched_mc == 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) { OK, it is :) (for the question above). Where do we utilize the set sched_mc_preferred_wakeup_cpu? > + cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu = > + first_cpu(group_leader->cpumask); Everytime we balance, we keep replacing rd->sched_mc_preferred_wake_up with group_lead->cpumask? My big concern is that we do this without checking if the group_leader has sufficient capacity (after it will pull in tasks since we made the checks for nr_running and capacity). > + } > return group_min; > } > #endif > > -- Balbir