From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: PROBLEM: Cpufreq constantly keeps frequency at maximum on 4.5-rc4 Date: Mon, 22 Feb 2016 11:46:37 +0530 Message-ID: <20160222061637.GF28226@vireshk-i7> References: <87egc7ahqn.fsf@iki.fi> <000401d16bfc$21338450$639a8cf0$@net> <87a8mv9ujm.fsf@iki.fi> <36DF59CE26D8EE47B0655C516E9CE640286C6253@shsmsx102.ccr.corp.intel.com> <87egc6zc2q.fsf@iki.fi> <36DF59CE26D8EE47B0655C516E9CE640286C6319@shsmsx102.ccr.corp.intel.com> <56CA17D4.8080802@linux.intel.com> <87lh6du7lu.fsf@iki.fi> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pa0-f48.google.com ([209.85.220.48]:36331 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774AbcBVGQ4 (ORCPT ); Mon, 22 Feb 2016 01:16:56 -0500 Received: by mail-pa0-f48.google.com with SMTP id yy13so85628766pab.3 for ; Sun, 21 Feb 2016 22:16:55 -0800 (PST) Content-Disposition: inline In-Reply-To: <87lh6du7lu.fsf@iki.fi> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Arto Jantunen Cc: Srinivas Pandruvada , "Chen, Yu C" , Doug Smythies , "'Rafael J. Wysocki'" , "linux-pm@vger.kernel.org" On 21-02-16, 22:33, Arto Jantunen wrote: > Srinivas Pandruvada writes: > >>> Powersave: > >>> /sys/devices/system/cpu/intel_pstate/max_perf_pct:100 > >>> /sys/devices/system/cpu/intel_pstate/min_perf_pct:22 > >>> > >>> Performance: > >>> /sys/devices/system/cpu/intel_pstate/max_perf_pct:100 > >>> /sys/devices/system/cpu/intel_pstate/min_perf_pct:100 > >>> > >>> Also, adding intel_pstate=no_hwp to the command line does not change the > >>> result. Changing that to intel_pstate=disable does fix the problem, so the > >>> bug seems to be somewhere in intel_pstate instead of cpufreq core. > > You have Skylake, which is not compatible with legacy ACPI P states with _PSS > > tables, so not running without intel_pstate is not much use. It may be running > > at at low P-state by disabling. > > > > Is Debian use default mode as performance? I think Ubuntu uses performance > > mode as default. > > What is the output of > > cat cpu*/cpufreq/scaling_governor > > I have tested both available governors, and see the same behavior either > way. The kernel I have defaults to performance, I think I'll try > building another one which defaults to powersave to see if that changes > anything (perhaps both governors actually work but it isn't possible to > switch between them at runtime?). The Debian userspace defaults to > ondemand, which doesn't exist for intel_pstate. I took a close look at git log between 4.4 and 4.5-rc1 for intel-pstate and it had only three patches: 157386b6fc14 cpufreq: intel_pstate: Configurable algorithm to get target pstate e70eed2b6454 cpufreq: intel_pstate: Account for non C0 time 63d1d656a523 cpufreq: intel_pstate: Account for IO wait time The first one creates special routines based on the CPU model you have, yours is 94, i.e. 5e, which means we are going to use: core_params in your case. And so you will be using get_target_pstate_use_performance() for .get_target_pstate(). The two later patches doesn't make any changes to the working of core_params() and so shouldn't have changed anything for skylake. Anyway, Please trying reverting the above three patches to see if there is a bug somewhere there. So you need to do: git revert 63d1d656a523 git revert e70eed2b6454 git revert 157386b6fc14 -- viresh