From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754984AbcASNrw (ORCPT ); Tue, 19 Jan 2016 08:47:52 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:52165 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754294AbcASNrn (ORCPT ); Tue, 19 Jan 2016 08:47:43 -0500 Date: Tue, 19 Jan 2016 14:47:39 +0100 From: Peter Zijlstra To: Luca Abeni Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Juri Lelli Subject: Re: [RFC 4/8] Improve the tracking of active utilisation Message-ID: <20160119134739.GY6357@twins.programming.kicks-ass.net> 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> <569E29FD.9040909@unitn.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <569E29FD.9040909@unitn.it> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 19, 2016 at 01:20:13PM +0100, Luca Abeni wrote: > 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? Correct. > If this understanding is correct (modulo some details that I'll figure out > during testing), I'll try this. Yes, there's bound to be 'fun' details.. > 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. urgh, yes.. details :-)