From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754619AbbLPNuH (ORCPT ); Wed, 16 Dec 2015 08:50:07 -0500 Received: from casper.infradead.org ([85.118.1.10]:38070 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752546AbbLPNuF (ORCPT ); Wed, 16 Dec 2015 08:50:05 -0500 Date: Wed, 16 Dec 2015 14:50:01 +0100 From: Peter Zijlstra To: Jirka Hladky Cc: Rik van Riel , Mike Galbraith , linux-kernel@vger.kernel.org, Ingo Molnar , "kkolakow@redhat.com" Subject: Re: sched : performance regression 24% between 4.4rc4 and 4.3 kernel Message-ID: <20151216135001.GO6357@twins.programming.kicks-ass.net> References: <1449903863.9638.8.camel@gmail.com> <1449931045.7411.8.camel@gmail.com> <566F7715.3020905@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 16, 2015 at 01:56:17PM +0100, Jirka Hladky wrote: > Hi Rik, > > I have redone the bisecting and have new results: > > # first bad commit: [2a595721a1fa6b684c1c818f379bef834ac3d65e] > sched/numa: Convert sched_numa_balancing to a static_branch > > Could you please have a look what went wrong? The below is obviously wrong, but your kernel should have that patch. So if you revert this patch (ie. go back to the regular variable) it works again? --- commit b52da86e0ad58f096710977fcda856fd84da9233 Author: Srikar Dronamraju Date: Fri Oct 2 07:48:25 2015 +0530 sched/numa: Fix task_tick_fair() from disabling numa_balancing If static branch 'sched_numa_balancing' is enabled, it should kickstart NUMA balancing through task_tick_numa(). However the following commit: 2a595721a1fa ("sched/numa: Convert sched_numa_balancing to a static_branch") erroneously disables this. Fix this anomaly by enabling task_tick_numa() when the static branch 'sched_numa_balancing' is enabled. Signed-off-by: Srikar Dronamraju Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mel Gorman Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1443752305-27413-1-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4df37a48f499..3bdc3da7bc6a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7881,7 +7881,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) entity_tick(cfs_rq, se, queued); } - if (!static_branch_unlikely(&sched_numa_balancing)) + if (static_branch_unlikely(&sched_numa_balancing)) task_tick_numa(rq, curr); }