Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760285Ab3GZVDf (ORCPT ); Fri, 26 Jul 2013 17:03:35 -0400 Received: from merlin.infradead.org ([205.233.59.134]:50617 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760155Ab3GZVDc (ORCPT ); Fri, 26 Jul 2013 17:03:32 -0400 Date: Fri, 26 Jul 2013 23:03:17 +0200 From: Peter Zijlstra To: Paul Turner Cc: Max Hailperin , LKML , Ingo Molnar Subject: Re: PROBLEM: Persistent unfair sharing of a processor by auto groups in 3.11-rc2 (has twice regressed) Message-ID: <20130726210317.GC20909@twins.programming.kicks-ass.net> References: <9E84D12D-7389-4D9A-803A-91FD704A92FA@gustavus.edu> <20130725112123.GT27075@twins.programming.kicks-ass.net> <228E8D34-E1A9-4D82-B353-F095E473B8D7@gustavus.edu> <20130725164051.GZ27075@twins.programming.kicks-ass.net> <20130725211521.GE18254@gmail.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 Content-Length: 1739 Lines: 51 OK, so I have the below; however on a second look, Paul, shouldn't that update_cfs_shares() call be in entity_tick(), right after calling update_cfs_rq_blocked_load(). Because placing it in update_cfs_rq_blocked_load() means its now called twice on the enqueue/dequeue paths through: {en,de}queue_entity() {en,de}queue_entity_load_avg() update_cfs_rq_blocked_load() update_cfs_shares() --- Subject: sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks From: Max Hailperin We typically update a task_group's shares within the dequeue/enqueue path. However, continuously running tasks sharing a CPU are not subject to these updates as they are only put/picked. Unfortunately, when we reverted f269ae046 (in 17bc14b7), we lost the augmenting periodic update that was supposed to account for this; resulting in a potential loss of fairness. To fix this, re-introduce the explicit update in update_cfs_rq_blocked_load() [called via entity_tick()]. Cc: stable@kernel.org Reviewed-by: Paul Turner Signed-off-by: Peter Zijlstra --- kernel/sched/fair.c | 1 + 1 file changed, 1 insertion(+) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1531,6 +1531,7 @@ static void update_cfs_rq_blocked_load(s } __update_cfs_rq_tg_load_contrib(cfs_rq, force_update); + update_cfs_shares(cfs_rq); } static inline void update_rq_runnable_avg(struct rq *rq, int runnable) -- 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/