From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: Ask for help on governor Date: Tue, 12 Dec 2017 17:51:25 +0100 Message-ID: References: <000801d37364$d48f6ed0$7dae4c70$@net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Received: from mail-ot0-f175.google.com ([74.125.82.175]:45191 "EHLO mail-ot0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752102AbdLLQv0 (ORCPT ); Tue, 12 Dec 2017 11:51:26 -0500 Received: by mail-ot0-f175.google.com with SMTP id 103so18337275otj.12 for ; Tue, 12 Dec 2017 08:51:26 -0800 (PST) In-Reply-To: <000801d37364$d48f6ed0$7dae4c70$@net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Doug Smythies Cc: Viresh Kumar , Andy Tang , "Rafael J. Wysocki" , Linux PM On Tue, Dec 12, 2017 at 5:18 PM, Doug Smythies wrote: > On 2017.12.11 23:31 Viresh Kumar wrote: >> On 12-12-17, 02:46, Andy Tang wrote: >>> Hi, >>> >>> I run into a question that conservative governor can't work while ondemand governor works well. >>> When cpu load gets higher, if ondemand governor is used, cpu frequency can get higher and higher. >>> But if I use conservative governor, cpu frequency stays on lowest frequency no matter what cpu load is. >>> >>> This issue was found on kernel 4.14.0, on kernel 4.9 kernel. It acts well. >> >> You mean to say that the problem exists on 4.14 but not on 4.9? >> >> Strange, as we haven't seen any such reports from anyone else. > > Well, it is easy enough for us to check. > Indeed, it is broken in kernel 4.14-rc1, but O.K. in kernel 4.13. > It remains broken in kernel 4.15-rc1 (I am not on -rc3 yet). > > Because it was easier for me to do so, I used intel_cpufreq (i.e. intel_pstate in passive mode). > >> >>> I think it may related to cpufreq framework, not driver itself. Could you guys give me some clues on how to debug it? >>> I don't expect a direct answer; any suggestions are welcome. >> >> Please provide output of below: >> >> grep . /sys/devices/system/cpu/cpufreq/policy*/* >> >> And then you may need to bisect the problem as well by going to kernel version >> in between 4.9 and 4.14. > > @Andy: Have you started bisecting the kernel yet? I suppose I could if you haven't, > or if you do not know how. There is only one commit touching conservative in 4.14: 2d045036322c cpufreq: governor: Drop min_sampling_rate Maybe try to revert this one?