From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752088AbaEZXKx (ORCPT ); Mon, 26 May 2014 19:10:53 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:63108 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751498AbaEZXKv (ORCPT ); Mon, 26 May 2014 19:10:51 -0400 From: "Rafael J. Wysocki" To: "Srivatsa S. Bhat" Cc: viresh.kumar@linaro.org, svaidy@linux.vnet.ibm.com, ego@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cpufreq: governor: Be friendly towards latency-sensitive bursty workloads Date: Tue, 27 May 2014 01:27:54 +0200 Message-ID: <2902116.OdbNv5KQzQ@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.15.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20140526205337.1100.55275.stgit@srivatsabhat.in.ibm.com> References: <20140526205337.1100.55275.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Srivatsa, On Tuesday, May 27, 2014 02:23:38 AM Srivatsa S. Bhat wrote: > Cpufreq governors like the ondemand governor calculate the load on the CPU > periodically by employing deferrable timers. A deferrable timer won't fire > if the CPU is completely idle (and there are no other timers to be run), in > order to avoid unnecessary wakeups and thus save CPU power. > > However, the load calculation logic is agnostic to all this, and this can > lead to the problem described below. This is subtle enough that I need some more time to chew on it, but since the merge window is coming, I'm not sure when that's going to happen honestly. Rafael