Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751609AbcDTW2m (ORCPT ); Wed, 20 Apr 2016 18:28:42 -0400 Received: from mga04.intel.com ([192.55.52.120]:5519 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751188AbcDTW2l (ORCPT ); Wed, 20 Apr 2016 18:28:41 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,511,1455004800"; d="scan'208";a="959366036" Subject: Re: [PATCH] sched/cpufreq: don't trigger cpufreq update w/o real rt/deadline tasks running To: Wanpeng Li References: <1460958684-32105-1-git-send-email-wanpeng.li@hotmail.com> <6087716.bi8vDPiZNy@vostro.rjw.lan> <20160420140117.GZ3448@twins.programming.kicks-ass.net> Cc: Peter Zijlstra , "Rafael J. Wysocki" , Ingo Molnar , "linux-kernel@vger.kernel.org" , Wanpeng Li , Linux PM list , Steve Muckle From: "Rafael J. Wysocki" Organization: Intel Technology Poland Sp. z o. o., KRS 101882, ul. Slowackiego 173, 80-298 Gdansk Message-ID: <57180293.1040809@intel.com> Date: Thu, 21 Apr 2016 00:28:35 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1401 Lines: 35 On 4/21/2016 12:24 AM, Wanpeng Li wrote: > 2016-04-20 22:01 GMT+08:00 Peter Zijlstra : >> On Wed, Apr 20, 2016 at 02:32:35AM +0200, Rafael J. Wysocki wrote: >>> On Monday, April 18, 2016 01:51:24 PM Wanpeng Li wrote: >>>> Sometimes update_curr() is called w/o tasks actually running, it is >>>> captured by: >>>> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; >>>> We should not trigger cpufreq update in this case for rt/deadline >>>> classes, and this patch fix it. >>>> >>>> Signed-off-by: Wanpeng Li >>> The signed-off-by tag should agree with the From: header. One way to achieve >>> that is to add an extra From: line at the start of the changelog. >>> >>> That said, this looks like a good catch that should go into 4.6 to me. >>> >>> Peter, what do you think? >> I'm confused by the Changelog. *what* ? > Sometimes .update_curr hook is called w/o tasks actually running, it is > captured by: > > u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; > > We should not trigger cpufreq update in this case for rt/deadline > classes, and this patch fix it. That's what you wrote in the changelog, no need to repeat that. I guess Peter is asking for more details, though. I actually would like to get some more details here too. Like an example of when the situation in question actually happens. Thanks, Rafael