Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933127Ab0BPR3O (ORCPT ); Tue, 16 Feb 2010 12:29:14 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:38325 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757017Ab0BPR3N (ORCPT ); Tue, 16 Feb 2010 12:29:13 -0500 Subject: Re: [patch] sched: fix SMT scheduler regression in find_busiest_queue() From: Peter Zijlstra To: svaidy@linux.vnet.ibm.com Cc: Suresh Siddha , Ingo Molnar , LKML , "Ma, Ling" , "Zhang, Yanmin" , ego@in.ibm.com In-Reply-To: <20100216155906.GC8777@dirshya.in.ibm.com> References: <1266023662.2808.118.camel@sbs-t61.sc.intel.com> <20100213182748.GB5882@dirshya.in.ibm.com> <20100213202552.GI5882@dirshya.in.ibm.com> <20100213203611.GJ5882@dirshya.in.ibm.com> <1266142318.5273.407.camel@laptop> <20100215123538.GE8006@dirshya.in.ibm.com> <1266238843.15770.323.camel@laptop> <20100216155906.GC8777@dirshya.in.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 16 Feb 2010 18:28:44 +0100 Message-ID: <1266341325.9432.283.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3102 Lines: 69 On Tue, 2010-02-16 at 21:29 +0530, Vaidyanathan Srinivasan wrote: > Agreed. Placement control should be handled by SD_PREFER_SIBLING > and SD_POWER_SAVINGS flags. > > --Vaidy > > --- > > sched_smt_powersavings for threaded systems need this fix for > consolidation to sibling threads to work. Since threads have > fractional capacity, group_capacity will turn out to be one > always and not accommodate another task in the sibling thread. > > This fix makes group_capacity a function of cpumask_weight that > will enable the power saving load balancer to pack tasks among > sibling threads and keep more cores idle. > > Signed-off-by: Vaidyanathan Srinivasan > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 522cf0e..ec3a5c5 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -2538,9 +2538,17 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, > * In case the child domain prefers tasks go to siblings > * first, lower the group capacity to one so that we'll try > * and move all the excess tasks away. I prefer a blank line in between two paragraphs, but even better would be to place this comment at the else if site. > + * If power savings balance is set at this domain, then > + * make capacity equal to number of hardware threads to > + * accomodate more tasks until capacity is reached. The my spell checker seems to prefer: accommodate > + * default is fractional capacity for sibling hardware > + * threads for fair use of available hardware resources. > */ > if (prefer_sibling) > sgs.group_capacity = min(sgs.group_capacity, 1UL); > + else if (sd->flags & SD_POWERSAVINGS_BALANCE) > + sgs.group_capacity = > + cpumask_weight(sched_group_cpus(group)); I guess we should apply cpu_active_mask so that we properly deal with offline siblings, except with cpumasks being the beasts they are I see no cheap way to do that. > if (local_group) { > sds->this_load = sgs.avg_load; > @@ -2855,7 +2863,8 @@ static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle) > !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE)) > return 0; > > - if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP) > + if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP && > + sched_smt_power_savings < POWERSAVINGS_BALANCE_WAKEUP) > return 0; > } /me still hopes for that unification patch.. :-) -- 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/