From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754731Ab2DTOA0 (ORCPT ); Fri, 20 Apr 2012 10:00:26 -0400 Received: from casper.infradead.org ([85.118.1.10]:46936 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752524Ab2DTOAZ (ORCPT ); Fri, 20 Apr 2012 10:00:25 -0400 Subject: Re: load balancing regression since commit 367456c7 From: Peter Zijlstra To: Tim Chen Cc: Suresh Siddha , Alex Shi , Ying , linux-kernel In-Reply-To: <1334681054.3796.28.camel@schen9-DESK> References: <1334106376.19157.89.camel@schen9-DESK> <1334664553.28150.87.camel@twins> <1334681054.3796.28.camel@schen9-DESK> Content-Type: text/plain; charset="UTF-8" Date: Fri, 20 Apr 2012 16:00:21 +0200 Message-ID: <1334930421.2463.60.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-04-17 at 09:44 -0700, Tim Chen wrote: > On Tue, 2012-04-17 at 14:09 +0200, Peter Zijlstra wrote: > > On Tue, 2012-04-10 at 18:06 -0700, Tim Chen wrote: > > > |--56.52%-- load_balance > > > | idle_balance > > > | __schedule > > > | schedule > > > > Ahh, I know why I didn't see it, I have a CONFIG_PREEMPT kernel and > > idle_balancing stops once its gotten a single task over instead of > > achieving proper balance. > > > > And since hackbench generates insanely long runqueues and the patch that > > caused your regression 'fixed' the lock-breaking it will now iterate the > > entire runqueue if needed to achieve balance, which hurts. > > > > I think the patch I send ought to work, let me try disabling > > CONFIG_PREEMPT. > > -- > > yes, CONFIG_PREEMPT is turned off on my side. With the patch that you > sent, the slowed down went from a factor of 4 down to a factor 2. > > So the run time is now twice as long vs four time as long vs v3.3 > kernel. Ok, so I can't reproduce this on my WSM-EP.. even !PREEMPT kernels are consistent with hackbench times with or without that patch. Can you still send your full .config? Also, do you have cpu-cgroup muck enabled and are you using that systemd shite? What does the below patch (on top of the previous) do? --- --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -784,7 +784,7 @@ account_entity_enqueue(struct cfs_rq *cf update_load_add(&rq_of(cfs_rq)->load, se->load.weight); #ifdef CONFIG_SMP if (entity_is_task(se)) - list_add_tail(&se->group_node, &rq_of(cfs_rq)->cfs_tasks); + list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks); #endif cfs_rq->nr_running++; }