Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755029AbcDATyN (ORCPT ); Fri, 1 Apr 2016 15:54:13 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:36507 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750750AbcDATyL convert rfc822-to-8bit (ORCPT ); Fri, 1 Apr 2016 15:54:11 -0400 MIME-Version: 1.0 In-Reply-To: <003801d18c44$ab9134e0$02b39ea0$@net> References: <2727017.UmaUvtBLeX@vostro.rjw.lan> <3623107.tlAuqH4F7s@vostro.rjw.lan> <1459532674.13525.136.camel@linux.intel.com> <003801d18c44$ab9134e0$02b39ea0$@net> Date: Fri, 1 Apr 2016 21:54:08 +0200 X-Google-Sender-Auth: zLtN0LgOkEpWZ9DoyT4dqRIVJeI Message-ID: Subject: Re: [intel-pstate driver regression] processor frequency very high even if in idle From: "Rafael J. Wysocki" To: Doug Smythies Cc: Srinivas Pandruvada , =?UTF-8?Q?J=C3=B6rg_Otte?= , "Rafael J. Wysocki" , "Rafael J. Wysocki" , Linux Kernel Mailing List , Linux PM list Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1567 Lines: 41 On Fri, Apr 1, 2016 at 8:31 PM, Doug Smythies wrote: > On 2106.034.01 10:45 Srinivas Pandruvada wrote: >> On Fri, 2016-04-01 at 16:06 +0200, Jörg Otte wrote: >> > > > > > >>> Done. Attached the tracer. >>> For me it looks like the previous one of the failing case. >> >> The traces show that idle task is constantly running without sleep. > > No, they (at least the first one, I didn't look at the next one yet) > show that CPUs 2 and 3 are spending around 99% of their time not in state > C0. How do you figure that out if I may ask? It is not so obvious to me to be honest. > That the sample rate is ending up at ~10 Milliseconds, indicates some > high frequency (>= 100Hz) events on those CPUs. Those events, apparently, > take very little CPU time to complete, hence a load of about 1% on average. > > By the way, I can recreate the high sample rate with virtually no load > on my system easy, but so far have been unable to get the high CPU > frequencies observed by Jörg. I can get my system to about a target pstate of > 20 where it should have remained at 16, but that is about it. > >> The driver is processing samples for idle task for every 10ms and >> aperf/mperf are showing that we are always in turbo mode for idle task. > > That column pretty much always says "idle" (or swapper for my way of doing > things). I have not found it to very useful as an indicator, and considerably > more so since the utilization changes. > >> >> Need to find out why idle task is not sleeping. > > I contend that is it. Why? Thanks, Rafael