From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: Delayed acpi frequency governor call Date: Tue, 24 Jan 2017 09:52:35 +0530 Message-ID: <20170124042235.GA16906@vireshk-i7> References: <20170120100725.GO11478@vireshk-i7> <9b332b49-11a1-a5fc-d48e-2c113cdca202@tik.ee.ethz.ch> <20170123101145.GB26681@vireshk-i7> <086bc55f-d1cc-b893-49c6-1667f6067f1b@tik.ee.ethz.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pf0-f173.google.com ([209.85.192.173]:32809 "EHLO mail-pf0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750703AbdAXE2n (ORCPT ); Mon, 23 Jan 2017 23:28:43 -0500 Received: by mail-pf0-f173.google.com with SMTP id y143so46792552pfb.0 for ; Mon, 23 Jan 2017 20:28:43 -0800 (PST) Content-Disposition: inline In-Reply-To: <086bc55f-d1cc-b893-49c6-1667f6067f1b@tik.ee.ethz.ch> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Philipp Miedl Cc: alex@digriz.org.uk, jun.nakajima@intel.com, venkatesh.pallipadi@intel.com, "linux-pm@vger.kernel.org" On 23-01-17, 15:24, Philipp Miedl wrote: > I would say it only checks whether the elapsed time since the last governor > call. My question is whether the call to the governor can be delayed for > such a long time without the CPU going into idle? If it can be guaranteed > that the governor call cannot be delayed without the CPU going to idle than > it is true - otherwise not. You are using a 4.4 kernel, which used the older delayed work stuff at sampling rate. This has all changed a lot and we hooks paired with the scheduler now to do this instead. Things have mostly changed since 4.7. Would it be possible for you to use a later kernel and see if you still see something wrong? Now coming back to 4.4, the timers (in the delayed works) can't get delayed but the work can as it is just another process. But your setup has no almost load and that seems unlikely as well. So, it looks to be a problem at some other place. Tracers are your friend, only those can confirm something here. -- viresh