Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751719AbZIBL3Z (ORCPT ); Wed, 2 Sep 2009 07:29:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751468AbZIBL3Y (ORCPT ); Wed, 2 Sep 2009 07:29:24 -0400 Received: from e28smtp07.in.ibm.com ([59.145.155.7]:42489 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbZIBL3Y (ORCPT ); Wed, 2 Sep 2009 07:29:24 -0400 Date: Wed, 2 Sep 2009 16:59:10 +0530 From: Gautham R Shenoy To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Andreas Herrmann , Balbir Singh Subject: Re: [RFC][PATCH 7/8] sched: try to deal with low capacity Message-ID: <20090902112910.GF3817@in.ibm.com> Reply-To: ego@in.ibm.com References: <20090901083431.748830771@chello.nl> <20090901083826.342231003@chello.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090901083826.342231003@chello.nl> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2316 Lines: 72 On Tue, Sep 01, 2009 at 10:34:38AM +0200, Peter Zijlstra wrote: > When the capacity drops low, we want to migrate load away. Allow the > load-balancer to remove all tasks when we hit rock bottom. > > Signed-off-by: Peter Zijlstra > --- > kernel/sched.c | 33 ++++++++++++++++++++++++++++----- > 1 file changed, 28 insertions(+), 5 deletions(-) > > Index: linux-2.6/kernel/sched.c > =================================================================== > --- linux-2.6.orig/kernel/sched.c > +++ linux-2.6/kernel/sched.c > @@ -3908,8 +3908,8 @@ static inline void update_sg_lb_stats(st > if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task) > sgs->group_imb = 1; > > - sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE; > - > + sgs->group_capacity = > + DIV_ROUND_CLOSEST(group->__cpu_power, SCHED_LOAD_SCALE); > } > > /** > @@ -3959,7 +3959,7 @@ static inline void update_sd_lb_stats(st > * and move all the excess tasks away. > */ > if (prefer_sibling) > - sgs.group_capacity = 1; > + sgs.group_capacity = min(sgs.group_capacity, 1UL); Ok, this means that sgs.group_capacity can now be 0, if for some reason group->__cpu_power happens to be less than SCHED_LOAD_SCALE/2. In that case, we need the following hunk to make it work for update_sd_power_savings_stats(). That's because both sum_nr_running and group_capacity are unsigned longs. ----> diff --git a/kernel/sched.c b/kernel/sched.c index 12fdbb8..9952292 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3580,7 +3580,7 @@ static inline void update_sd_power_savings_stats(struct sched_group *group, * capacity but still has some space to pick up some load * from other group and save more power */ - if (sgs->sum_nr_running > sgs->group_capacity - 1) + if (sgs->sum_nr_running + 1 > sgs->group_capacity) return; if (sgs->sum_nr_running > sds->leader_nr_running || ----> > > if (local_group) { > sds->this_load = sgs.avg_load; > @@ -4191,6 +4191,26 @@ ret: > return NULL; > } > -- Thanks and Regards gautham -- 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/