From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH] cpufreq: schedutil: Always trace frequency if it does not change Date: Wed, 22 Mar 2017 10:29:51 +0100 Message-ID: <20170322092951.GX5680@worktop> References: <10655562.4O9KtquB0A@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from merlin.infradead.org ([205.233.59.134]:44144 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759040AbdCVJ37 (ORCPT ); Wed, 22 Mar 2017 05:29:59 -0400 Content-Disposition: inline In-Reply-To: <10655562.4O9KtquB0A@aspire.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Linux PM , LKML , Viresh Kumar , Patrick Bellasi , Vincent Guittot On Wed, Mar 22, 2017 at 01:56:53AM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > sugov_update_commit() calls trace_cpu_frequency() to record the > current CPU frequency if it has not changed in the fast switch case > to prevent utilities from getting confused (they may report that the > CPU is idle if the frequency has not been recorded for too long, for > example). That seems like buggy tools; we should then fix the tools, not the kernel to emit more superfluous information. > However, the same problem may occur for a cpufreq driver that doesn't > support fast frequency switching and implements the ->target callback > (that is, it doesn't use frequency tables), but trace_cpu_frequency() > is not called if frequency updates are skipped in that case. I'm having trouble parsing that; am I right in understanding this is the exact same scenario where only superfluous changes are omitted? > For this reason, modify sugov_update_commit() to always call > trace_cpu_frequency() when the new frequency to be set is equal to > the one that was set previously and reorganize the code in there to > reduce duplication somewhat. So why not fix the tools?