From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Doug Smythies" Subject: RE: [intel-pstate driver regression] processor frequency very high even if in idle Date: Wed, 30 Mar 2016 11:50:35 -0700 Message-ID: <002401d18ab5$0bf84a30$23e8de90$@net> References: <4187911.uaFVupaTVL@vostro.rjw.lan> <1459352017.13525.45.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cmta8.telus.net ([209.171.16.81]:48194 "EHLO cmta8.telus.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754563AbcC3Sul convert rfc822-to-8bit (ORCPT ); Wed, 30 Mar 2016 14:50:41 -0400 In-Reply-To: Content-Language: en-ca Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: =?UTF-8?Q?'J=C3=B6rg_Otte'?= , "'Pandruvada, Srinivas'" Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rjw@rjwysocki.net On 2016.03.30 08:52 J=C3=B6rg Otte wrote: > 2016-03-30 17:33 GMT+02:00 Pandruvada, Srinivas : >> On Wed, 2016-03-30 at 13:05 +0200, Rafael J. Wysocki wrote: >>> On Wed, Mar 30, 2016 at 12:17 PM, J=C3=B6rg Otte >>>>>> Now in v4.6-rc1 the characteristic has dramatically changed. >>>>>> If in idle the processor frequency is more or less a few >>>>>> MHz around 2500Mhz. >>>>>> I currently use acpi_cpufreq which works as usual. >>>>>> Processor: Intel(R) Core(TM) i5-4200M CPU @ 2.50GHz >>>>>> (family: 0x6, model: 0x3c, stepping: 0x3) >> I want to reproduce this if I can. Can you give us info about your >> setup (Linux distribution, laptop model etc.)? I would like to try to reproduce the issue also. > Distro: Ubuntu 14.04.4 LTS Note that with Ubuntu 14.04, I had issues where my CPU would lock at pstate 24 (not always 24, but usually), regardless of load. However, it was always after an S3 suspend, occurred 100% of the time, and was independent of intel_pstate or acpi-cpufreq CPU frequency scaling drivers. Since changing my test server to Ubuntu server edition 16.04 (development version), I have not had those issues. While I have no proof, I have assumed the issue elimination was somehow related to the change to systemd. It might be worth observing both what the intel_pstate is asking for and what the processor is actually doing. What is being asked for: # rdmsr --bitfield 15:8 -d -a 0x199 What is being given: # rdmsr --bitfield 15:8 -d -a 0x198 An old problematic example from an idle system (mine) Note, my minimum pstate is 16: What was being given: # rdmsr --bitfield 15:8 -d -a 0x198 24 24 24 24 24 24 24 24 What was being asked for: # rdmsr --bitfield 15:8 -d -a 0x199 16 16 16 16 16 16 16 16 To gain further insight, it might also be worth acquiring some trace data. On an otherwise idle system, do: # perf record -a --event=3Dpower:pstate_sample sleep 300 If pressed for time, your sleep time can be less than 5 minutes, but try to get at least 100 seconds. The resulting perf.data file will be too big to include as an on-list attachment, but send it (or them) to me off-list for post processing, and I'll report back. =2E.. Doug