From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [PATCH] cpufreq: governor: Be friendly towards latency-sensitive bursty workloads Date: Tue, 27 May 2014 08:45:52 +0530 Message-ID: <53840368.4030004@linux.vnet.ibm.com> References: <20140526205337.1100.55275.stgit@srivatsabhat.in.ibm.com> <2902116.OdbNv5KQzQ@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from e23smtp05.au.ibm.com ([202.81.31.147]:39724 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751466AbaE0DRK (ORCPT ); Mon, 26 May 2014 23:17:10 -0400 Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 27 May 2014 13:17:08 +1000 In-Reply-To: <2902116.OdbNv5KQzQ@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" 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 On 05/27/2014 04:57 AM, Rafael J. Wysocki wrote: > 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. > Sure, I completely understand. Please take your time, no hurry! Thank you very much! Regards, Srivatsa S. Bhat