From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753817AbcASMUT (ORCPT ); Tue, 19 Jan 2016 07:20:19 -0500 Received: from mail-wm0-f54.google.com ([74.125.82.54]:33813 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753033AbcASMUQ (ORCPT ); Tue, 19 Jan 2016 07:20:16 -0500 Subject: Re: [RFC 4/8] Improve the tracking of active utilisation To: Peter Zijlstra References: <1452785094-3086-1-git-send-email-luca.abeni@unitn.it> <1452785094-3086-5-git-send-email-luca.abeni@unitn.it> <20160114194323.GC6357@twins.programming.kicks-ass.net> Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Juri Lelli From: Luca Abeni Message-ID: <569E29FD.9040909@unitn.it> Date: Tue, 19 Jan 2016 13:20:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20160114194323.GC6357@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 01/14/2016 08:43 PM, Peter Zijlstra wrote: > On Thu, Jan 14, 2016 at 04:24:49PM +0100, Luca Abeni wrote: >> This patch implements a more theoretically sound algorithm for >> thracking the active utilisation: instead of decreasing it when a >> task blocks, use a timer (the "inactive timer", named after the >> "Inactive" task state of the GRUB algorithm) to decrease the >> active utilisaation at the so called "0-lag time". > > See also the large-ish comment in __setparam_dl(). > > If we go do proper 0-lag, as GRUB requires, then we might as well use it > for that. Just to check if I understand correctly: I would need to remove "dl_b->total_bw -= p->dl.dl_bw;" from task_dead_dl(), and __dl_clear() from "else if (!dl_policy(policy) && task_has_dl_policy(p))" in dl_overflow(). Then, arm the inactive_timer in these cases, and add the __dl_clear() in the "if (!dl_task(p))" in inactive_task_timer()... Right? If this understanding is correct (modulo some details that I'll figure out during testing), I'll try this. In theory, the inactive_timer would be the right place to also decrease the active utilisation when a task switches from SCHED_DEADLINE to something else... But this is problematic if the task migrates after switching from SCHED_DEADLINE and before the timer fires. Thanks, Luca