From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754863AbcC1S5L (ORCPT ); Mon, 28 Mar 2016 14:57:11 -0400 Received: from smtprelay0139.hostedemail.com ([216.40.44.139]:47634 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751639AbcC1S5H (ORCPT ); Mon, 28 Mar 2016 14:57:07 -0400 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2198:2199:2393:2553:2559:2562:2693:2731:3138:3139:3140:3141:3142:3352:3622:3865:3866:3867:3868:3870:3871:3872:3873:4250:4321:5007:6120:6261:7875:7903:10004:10400:10450:10455:10848:10967:11232:11658:11914:12517:12519:12740:13069:13311:13357:13439:14096:14097:14180:14181:14659:14721:19904:19999:21060:21080:21324:30054:30055:30090:30091,0,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: sun75_3db1c915c3503 X-Filterd-Recvd-Size: 2280 Date: Mon, 28 Mar 2016 14:57:02 -0400 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Josh Cartwright , Daniel Wagner , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, "Peter Zijlstra (Intel)" , Thomas Gleixner , Daniel Wagner Subject: Re: [RFC v0] Use swait in completion Message-ID: <20160328145702.589da4bd@gandalf.local.home> In-Reply-To: <20160309122423.GD10517@linutronix.de> References: <1457452754-24029-1-git-send-email-wagi@monom.org> <20160308175206.GD21842@linutronix.de> <20160308182656.GA27081@jcartwri.amer.corp.natinst.com> <20160309122423.GD10517@linutronix.de> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; 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 On Wed, 9 Mar 2016 13:24:23 +0100 Sebastian Andrzej Siewior wrote: > * Josh Cartwright | 2016-03-08 12:26:56 [-0600]: > > >Is it really just about latency? Does this deferral not lead to an > >inversion in the case where the single woken task isn't the highest > >priority waiter on the completion (and doesn't run due to a > >middle-priority thing spinning)? > > This would be case, yes. Not only with deferral. Say you have two > waters: 1st one is MID-prio and the second is HI-prio. Currently after > the wakeup of the MID-prio waiter you get preempted. Waking all of them > at once would put the second waiter first on the CPU. > Samething without the deferral flag. > > >In order for this to work, it seems like the chosen waiter would need to > >inherit the highest priority of all waiters (which AFAICT isn't > >happening). > > sorting the waiters by priority? This will be fun. This is only done for > the rtmutex waiters. > Hmm, perhaps we should use an rbtree to sort simple waiters by priority :-) Probably wont make them simple anymore. -- Steve