From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755107AbeCVNT3 (ORCPT ); Thu, 22 Mar 2018 09:19:29 -0400 Received: from mailout5.zih.tu-dresden.de ([141.30.67.74]:58815 "EHLO mailout5.zih.tu-dresden.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752282AbeCVNT2 (ORCPT ); Thu, 22 Mar 2018 09:19:28 -0400 Subject: Re: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle_select() To: "Rafael J. Wysocki" CC: Linux PM , Peter Zijlstra , Frederic Weisbecker , "Thomas Gleixner" , Paul McKenney , Doug Smythies , Rik van Riel , "Aubrey Li" , Mike Galbraith , LKML References: <2390019.oHdSGtR3EE@aspire.rjw.lan> <1635957.yuHkCe9oyz@aspire.rjw.lan> From: Thomas Ilsche Message-ID: <642c6901-ad0d-b6b3-9ee9-3e0bd10aa610@tu-dresden.de> Date: Thu, 22 Mar 2018 14:18:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-ClientProxiedBy: MSX-L106.msx.ad.zih.tu-dresden.de (172.26.34.106) To MSX-L104.msx.ad.zih.tu-dresden.de (172.26.34.104) X-PMWin-Version: 4.0.3, Antivirus-Engine: 3.70.2, Antivirus-Data: 5.49 X-TUD-Virus-Scanned: mailout5.zih.tu-dresden.de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-03-21 23:15, Rafael J. Wysocki wrote: > On Wed, Mar 21, 2018 at 6:59 PM, Thomas Ilsche > wrote: >> On 2018-03-21 15:36, Rafael J. Wysocki wrote: >>> >>> >>> So please disregard this one entirely and take the v7.2 replacement >>> instead of it:https://patchwork.kernel.org/patch/10299429/ >>> >>> The current versions (including the above) is in the git branch at >>> >>> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \ >>> idle-loop-v7.2 >> >> >> With v7.2 (tested on SKL-SP from git) I see similar behavior in idle >> as with v5: several cores which just keep the sched tick enabled. >> Worse yet, some go only in C1 (not even C1E!?) despite sleeping the >> full sched tick. >> The resulting power consumption is ~105 W instead of ~ 70 W. >> >> https://wwwpub.zih.tu-dresden.de/~tilsche/powernightmares/v7_2_skl_sp_idle.png >> >> I have briefly ran v7 and I believe it was also affected. > > Then it looks like menu_select() stubbornly thinks that the idle > duration will be within the tick boundary on those cores. > > That may be because the bumping up of the correction factor in > menu_reflect() is too conservative or it may be necessary to do > something radical to measured_us in menu_update() in case of a tick > wakeup combined with a large next_timer_us value. > > For starters, please see if the attached patch (on top of the > idle-loop-v7.2 git branch) changes this behavior in any way. > The patch on top of idle-loop-v7.2 doesn't improve idle behavior on SKL-SP. Overall it is pretty erratic, I have not seen any regular patterns. Sometimes only few cpus are affected, here's a screenshot of almost all cpus being affected after a short burst workload. https://wwwpub.zih.tu-dresden.de/~tilsche/powernightmares/v7_2_reflect_skl_sp_idle.png