Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752815AbbGJGZp (ORCPT ); Fri, 10 Jul 2015 02:25:45 -0400 Received: from mga11.intel.com ([192.55.52.93]:49284 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752283AbbGJGZh (ORCPT ); Fri, 10 Jul 2015 02:25:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,445,1432623600"; d="scan'208";a="726241329" Date: Fri, 10 Jul 2015 06:34:02 +0800 From: Yuyang Du To: Morten Rasmussen Cc: Mike Galbraith , Peter Zijlstra , Rabin Vincent , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , Paul Turner , Ben Segall Subject: Re: [PATCH?] Livelock in pick_next_task_fair() / idle_balance() Message-ID: <20150709223402.GH5197@intel.com> References: <20150701145551.GA15690@axis.com> <20150701204404.GH25159@twins.programming.kicks-ass.net> <20150701232511.GA5197@intel.com> <1435824347.5351.18.camel@gmail.com> <20150702010539.GB5197@intel.com> <20150702114032.GA7598@e105550-lin.cambridge.arm.com> <20150702193702.GD5197@intel.com> <20150703093441.GA15477@e105550-lin.cambridge.arm.com> <20150705201241.GE5197@intel.com> <20150709135314.GA8668@e105550-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150709135314.GA8668@e105550-lin.cambridge.arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2168 Lines: 42 On Thu, Jul 09, 2015 at 02:53:14PM +0100, Morten Rasmussen wrote: > On Mon, Jul 06, 2015 at 04:12:41AM +0800, Yuyang Du wrote: > > Hi Morten, > > > > On Fri, Jul 03, 2015 at 10:34:41AM +0100, Morten Rasmussen wrote: > > > > > IOW, since task groups include blocked load in the load_avg_contrib (see > > > > > __update_group_entity_contrib() and __update_cfs_rq_tg_load_contrib()) the > > > > > imbalance includes blocked load and hence env->imbalance >= > > > > > sum(task_h_load(p)) for all tasks p on the rq. Which leads to > > > > > detach_tasks() emptying the rq completely in the reported scenario where > > > > > blocked load > runnable load. > > > > > > > > Whenever I want to know the load avg concerning task group, I need to > > > > walk through the complete codes again, I prefer not to do it this time. > > > > But it should not be that simply to say "the 118 comes from the blocked load". > > > > > > But the whole hierarchy of group entities is updated each time we enqueue > > > or dequeue a task. I don't see how the group entity load_avg_contrib is > > > not up to date? Why do you need to update it again? > > > > > > In any case, we have one task in the group hierarchy which has a > > > load_avg_contrib of 0 and the grand-grand parent group entity has a > > > load_avg_contrib of 118 and no additional tasks. That load contribution > > > must be from tasks which are no longer around on the rq? No? > > > > load_avg_contrib has WEIGHT inside, so the most I can say is: > > SE: 8f456e00's load_avg_contrib 118 = (its cfs_rq's runnable + blocked) / (tg->load_avg + 1) * tg->shares > > > > The tg->shares is probably 1024 (at least 911). So we are just left with: > > > > cfs_rq / tg = 11.5% > > Yes, we also know that there is only one runnable task in the task group > hierarchy and its contribution is 0. Hence the rest must be from > non-runnable tasks belonging to some child group. Agreed. -- 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/