From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756261AbaJHMyr (ORCPT ); Wed, 8 Oct 2014 08:54:47 -0400 Received: from service87.mimecast.com ([91.220.42.44]:37022 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753293AbaJHMyq convert rfc822-to-8bit (ORCPT ); Wed, 8 Oct 2014 08:54:46 -0400 Message-ID: <54353422.3070002@arm.com> Date: Wed, 08 Oct 2014 13:54:58 +0100 From: Dietmar Eggemann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Yuyang Du , Morten Rasmussen CC: "peterz@infradead.org" , "mingo@redhat.com" , "pjt@google.com" , "bsegall@google.com" , "vincent.guittot@linaro.org" , "nicolas.pitre@linaro.org" , "mturquette@linaro.org" , "rjw@rjwysocki.net" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/7] sched: Introduce scale-invariant load tracking References: <1411403047-32010-1-git-send-email-morten.rasmussen@arm.com> <1411403047-32010-2-git-send-email-morten.rasmussen@arm.com> <20141008005007.GA7017@intel.com> In-Reply-To: <20141008005007.GA7017@intel.com> X-OriginalArrivalTime: 08 Oct 2014 12:54:43.0560 (UTC) FILETIME=[07F91E80:01CFE2F7] X-MC-Unique: 114100813544400301 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Yuyang, On 08/10/14 01:50, Yuyang Du wrote: > Hi Morten, > > Sorry for late jumping in. > > The problem seems to be self-evident. But for the implementation to be > equally attractive it needs to account for every freq change for every task, > or anything less than that makes it less attractive. > > But this should be very hard. Intel Architecture has limitation to capture all > the freq changes in software and also the intel_pstate should have no > notification. We encountered this missing notification for current frequency with Intel systems (e.g. i5-3320M) using the intel_pstate driver while testing this patch-set. The arch_scale_set_curr_freq call in __cpufreq_notify_transition [[PATCH 2/7] cpufreq: Architecture specific callback for frequency changes] will not work on such a system. In our internal testing, we placed arch_scale_set_curr_freq(cpu->cpu, sample->freq) into intel_pstate_timer_func [intel_pstate.c] to get the current frequency for a cpu. The arch_scale_set_max_freq call in cpufreq_set_policy [drivers/cpufreq/cpufreq.c] still works although the driver exposes the max turbo pstate and not the max pstate. That's an additional problem because we don't want to use turbo states for frequency scaling. > > For every task, this makes the updating of the entire queue in load tracking > more needed, so once again, ping maintainers for the rewrite patches, :) > > Thanks, > Yuyang > [...]