Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752074AbcKGUAJ (ORCPT ); Mon, 7 Nov 2016 15:00:09 -0500 Received: from smtprelay0252.hostedemail.com ([216.40.44.252]:45340 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750905AbcKGUAI (ORCPT ); Mon, 7 Nov 2016 15:00:08 -0500 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:2691:2693:3138:3139:3140:3141:3142:3353:3622:3865:3866:3867:3868:3871:3872:3874:4250:5007:6261:7875:10004:10400:10848:10967:11232:11658:11914:12296:12740:12760:13069:13161:13229:13311:13357:13439:14096:14097:14181:14659:14721:21080:30054:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:2,LUA_SUMMARY:none X-HE-Tag: shoes44_751add6a31926 X-Filterd-Recvd-Size: 2337 Date: Mon, 7 Nov 2016 15:00:03 -0500 From: Steven Rostedt To: Christoph Lameter Cc: Daniel Bristot de Oliveira , Ingo Molnar , Peter Zijlstra , linux-rt-users , LKML Subject: Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Message-ID: <20161107150003.66777b43@gandalf.local.home> In-Reply-To: References: <20161107133207.4282de69@gandalf.local.home> <20161107144738.4811a5dd@gandalf.local.home> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1048 Lines: 28 On Mon, 7 Nov 2016 13:54:12 -0600 (CST) Christoph Lameter wrote: > On Mon, 7 Nov 2016, Steven Rostedt wrote: > > > On Mon, 7 Nov 2016 13:30:15 -0600 (CST) > > Christoph Lameter wrote: > > > > > SCHED_RR tasks alternately running on on cpu can cause endless deferral of > > > kworker threads. With the global effect of the OS processing reserved > > > it may be the case that the processor we are executing never gets any > > > time. And if that kworker threads role is releasing a mutex (like the > > > cgroup_lock) then deadlocks can result. > > > > I believe SCHED_RR tasks will still throttle if they use up too much of > > the CPU. But I still don't see how this patch helps your situation. > > The kworker thread will be able to make progress? Or am I not reading this > correctly? > If kworker is SCHED_OTHER, then it will be able to make progress if the RT tasks are throttled. What Daniel's patch does, is to turn off throttling of the RT tasks if there's no other task on the run queue. -- Steve