Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757544AbYKWCEY (ORCPT ); Sat, 22 Nov 2008 21:04:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754949AbYKWCEP (ORCPT ); Sat, 22 Nov 2008 21:04:15 -0500 Received: from viefep18-int.chello.at ([213.46.255.22]:30258 "EHLO viefep18-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754410AbYKWCEP (ORCPT ); Sat, 22 Nov 2008 21:04:15 -0500 X-SourceIP: 213.46.9.244 Subject: Re: [RFC PATCH v4 3/7] sched: nominate preferred wakeup cpu From: Peter Zijlstra To: Vaidyanathan Srinivasan Cc: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Ingo Molnar , Dipankar Sarma , Balbir Singh , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Gregory Haskins In-Reply-To: <20081121083114.27075.2113.stgit@drishya.in.ibm.com> References: <20081121082533.27075.12056.stgit@drishya.in.ibm.com> <20081121083114.27075.2113.stgit@drishya.in.ibm.com> Content-Type: text/plain Date: Sun, 23 Nov 2008 03:03:58 +0100 Message-Id: <1227405838.7685.20000.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2591 Lines: 80 On Fri, 2008-11-21 at 14:01 +0530, Vaidyanathan Srinivasan wrote: > 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 > + > }; > > /* Do we really need that extra whitespace? > @@ -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 Ditto? > @@ -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); While not strictly needed, I prefer braces around multi-line statments. It's easier on the eyes. > 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/