From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752091AbdB1LgC (ORCPT ); Tue, 28 Feb 2017 06:36:02 -0500 Received: from foss.arm.com ([217.140.101.70]:36366 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751341AbdB1Lf7 (ORCPT ); Tue, 28 Feb 2017 06:35:59 -0500 Date: Tue, 28 Feb 2017 11:35:15 +0000 From: Juri Lelli To: Byungchul Park Cc: peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, rostedt@goodmis.org, kernel-team@lge.com Subject: Re: [PATCH v3] sched/deadline: Change the time to replenish runtime for sleep tasks Message-ID: <20170228113515.GM19665@e106622-lin> References: <1487830499-1691-1-git-send-email-byungchul.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1487830499-1691-1-git-send-email-byungchul.park@lge.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 23/02/17 15:14, Byungchul Park wrote: > Let's consider the following example. > > timeline : o...................o.........o.......o..o > ^ ^ ^ ^ ^ > | | | | | > start | | | | > original runtime | | | > sleep with (-)runtime | | > original deadline | > wake up > > When this task is woken up, a negative runtime should be considered, > which means that the task should get penalized when assigning runtime, > becasue it already spent more than expected. Current code handles this > by replenishing a runtime in hrtimer callback for deadline. But this > approach has room for improvement: > > It will be replenished twice unnecessarily if the task sleeps for > long time so that the deadline, assigned in the hrtimer callback, > also passed. In other words, one happens in the callback and the > other happens in update_dl_entiry() when waking it up. > > So force to replenish it for sleep tasks when waking it up. > > Signed-off-by: Byungchul Park > --- > kernel/sched/deadline.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 27737f3..cb43ce9 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -498,8 +498,9 @@ static void update_dl_entity(struct sched_dl_entity *dl_se, > struct dl_rq *dl_rq = dl_rq_of_se(dl_se); > struct rq *rq = rq_of_dl_rq(dl_rq); > > - if (dl_time_before(dl_se->deadline, rq_clock(rq)) || > - dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) { > + if (dl_time_before(dl_se->deadline, rq_clock(rq))) > + replenish_dl_entity(dl_se, pi_se); > + else if (dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) { > dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline; > dl_se->runtime = pi_se->dl_runtime; > } > @@ -621,13 +622,11 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) > * __dequeue_task_dl() > * prev->on_rq = 0; > * > - * We can be both throttled and !queued. Replenish the counter > - * but do not enqueue -- wait for our wakeup to do that. > + * We can be both throttled and !queued. Wait for our wakeup to > + * replenish runtime and enqueue p. > */ > - if (!task_on_rq_queued(p)) { > - replenish_dl_entity(dl_se, dl_se); Hasn't this patch the same problem we discussed a couple of weeks ago? https://marc.info/?l=linux-kernel&m=148699950802995 Thanks, - Juri