From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Doug Smythies" Subject: RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch Date: Wed, 7 Oct 2015 15:26:00 -0700 Message-ID: <001001d1014f$2613efe0$723bcfa0$@net> References: <1444168147-17812-1-git-send-email-prarit@redhat.com> <000f01d10131$59c67a60$0d536f20$@net> <56158F2D.50200@redhat.com> <10053399.aMfHfU7Xt3@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from cmta10.telus.net ([209.171.16.83]:58951 "EHLO cmta10.telus.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751020AbbJGW0D (ORCPT ); Wed, 7 Oct 2015 18:26:03 -0400 In-Reply-To: <10053399.aMfHfU7Xt3@vostro.rjw.lan> Content-Language: en-ca Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: 'Prarit Bhargava' Cc: 'Kristen Carlson Accardi' , linux-kernel@vger.kernel.org, 'Viresh Kumar' , linux-pm@vger.kernel.org, "'Rafael J. Wysocki'" , Doug Smythies On 2015.10.07 15:06 Rafael J. Wysocki wrote: > On Wednesday, October 07, 2015 05:31:25 PM Prarit Bhargava wrote: >> On 10/07/2015 02:52 PM, Doug Smythies wrote: >>> On 2015.10.07 08:46 Prarit Bhargava wrote: >>>> On 10/07/2015 11:40 AM, Doug Smythies wrote: >>>>> >>>>> Do we agree or disagree that the root issue seems to be (from your test)?: >>>>> >>>>> \# echo 100 > /sys/devices/system/cpu/intel_pstate/min_perf_pct >>>>> >>>>> [ 21.483436] store_min_perf_pct[453] min_sysfs_pct = 100 >>>>> [ 21.489373] store_min_perf_pct[456] min_perf_pct = 100 >>>>> [ 21.495203] store_min_perf_pct[459] min_perf_pct = 100 >>>>> [ 21.501050] store_min_perf_pct[462] min_perf_pct = 100 >>>> >>>> Yep, and it appears to be done by default in Fedora & RHEL :/ ... the issue is >>>> still the same IMO that min_sysfs_pct & max_sysfs_pct are not cleared on a >>>> governor switch. >>> >>> Clearing them will break some other things. For example, and as >>> shown in my original reply, resume from suspend. >>> >>> Why? Because, at least on my computer, the governor is changed to >>> "performance" during suspend, and the "powersave" governor is >>> restored sometime during resume. The users wants the settings they had >>> before the suspend. >>> >> Looking at this in more detail after having tested on a Intel(R) Core(TM) >> i7-2600 CPU @ 3.40GHz in Fedora and RHEL. >> >> I have a feeling that the switch you're seeing (poweersave->performance, suspend >> ... resume, performance->powersave) is occurring in userspace, and not as a >> result of the kernel. Agreed. It is pm-suspend doing it. >> IMO if userspace changes the governor, all bets are off >> on maintaining max_sysfs_pct and min_sysfs_pct. >> >> Here's something I cannot figure out (because I do not have an Ubuntu install). >> *Why* is Ubuntu making the governor switch during suspend/resume? Is it >> because of archaic brokeness they were trying to paper over? >> That's not limited to Ubuntu, pm-utils has been doing that forever. Agreed. This in pm-utils, and not limited to Ubuntu. We can ignore this issue if everyone wants, but I can envision bug reports. > I have no idea why has it been doing that, though. I guess the reason > was to "speed up" PM transitions (in case it started when you were in a > low-frequency P-state and then there was no time to bump it up before > things got too far). I have no idea either, but the stated theory seems sound.