From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96133C43382 for ; Thu, 27 Sep 2018 13:23:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56227216F4 for ; Thu, 27 Sep 2018 13:23:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56227216F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727674AbeI0TlR (ORCPT ); Thu, 27 Sep 2018 15:41:17 -0400 Received: from foss.arm.com ([217.140.101.70]:34572 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727262AbeI0TlR (ORCPT ); Thu, 27 Sep 2018 15:41:17 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AD5FC18A; Thu, 27 Sep 2018 06:23:01 -0700 (PDT) Received: from [0.0.0.0] (e107985-lin.emea.arm.com [10.4.12.239]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E6FBE3F5B7; Thu, 27 Sep 2018 06:22:52 -0700 (PDT) Subject: Re: [PATCH] sched/fair: vruntime should normalize when switching from fair To: Wanpeng Li Cc: Peter Zijlstra , Steve Muckle , Miguel de Dios , Ingo Molnar , LKML , kernel-team@android.com, Todd Kjos , Paul Turner , quentin.perret@arm.com, Patrick Bellasi , Chris.Redpath@arm.com, Morten Rasmussen , John Dias , Wanpeng Li References: <20180817182728.76129-1-smuckle@google.com> <20180824093227.GN24124@hirez.programming.kicks-ass.net> <20180824094742.GJ24142@hirez.programming.kicks-ass.net> <20180827111458.GB24124@hirez.programming.kicks-ass.net> <2ed346fa-dbe8-4928-928b-a34338b2d8c9@arm.com> <62134bba-b6bd-ba16-a49b-e4887c326559@arm.com> From: Dietmar Eggemann Message-ID: Date: Thu, 27 Sep 2018 15:22:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/27/2018 03:19 AM, Wanpeng Li wrote: > On Thu, 27 Sep 2018 at 06:38, Dietmar Eggemann wrote: >> >> Hi, >> >> On 09/26/2018 11:50 AM, Wanpeng Li wrote: >>> Hi Dietmar, >>> On Tue, 28 Aug 2018 at 22:55, Dietmar Eggemann wrote: >>>> >>>> On 08/27/2018 12:14 PM, Peter Zijlstra wrote: >>>>> On Fri, Aug 24, 2018 at 02:24:48PM -0700, Steve Muckle wrote: >>>>>> On 08/24/2018 02:47 AM, Peter Zijlstra wrote: >>>>>>>>> On 08/17/2018 11:27 AM, Steve Muckle wrote: >> >> [...] >> >>>>>>>>>> - later, when the prio is deboosted and the task is moved back >>>>>>>>>> to the fair class, the fair rq's min_vruntime is added to >>>>>>>>>> the task's vruntime, even though it wasn't subtracted earlier. >>> >>> Could you point out when the fair rq's min_vruntime is added to the >>> task's vruntime in your *later* scenario? attach_task_cfs_rq will not >>> do that the same reason as detach_task_cfs_rq. fair task's >>> sched_remote_wakeup is false which results in vruntime will not be >>> renormalized in enqueue_entity. >> >> The cfs_rq->min_vruntime is still added to the se->vruntime in >> enqueue_task_fair(). > > I understand what your patch done, It's not my patch ;-) I just helped to find out under which circumstances this issue can happen. > On your CPU4: > scheduler_ipi() > -> sched_ttwu_pending() > -> ttwu_do_activate() => p->sched_remote_wakeup should be > false, so ENQUEUE_WAKEUP is set, ENQUEUE_MIGRATED is not > -> ttwu_activate() > -> activate_task() > -> enqueue_task() > -> enqueue_task_fair() > -> enqueue_entity() > bool renorm = !(flags & > ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE) > so renorm is false in enqueue_entity(), why you mentioned that the > cfs_rq->min_vruntime is still added to the se->vruntime in > enqueue_task_fair()? Maybe this is a misunderstanding on my side but didn't you asked me to '... Could you point out when the fair rq's min_vruntime is added to the task's vruntime in your *later* scenario? ...'