From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030498AbcGKIQ1 (ORCPT ); Mon, 11 Jul 2016 04:16:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53729 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030341AbcGKIQX (ORCPT ); Mon, 11 Jul 2016 04:16:23 -0400 Reply-To: xlpang@redhat.com Subject: Re: [PATCH v3] sched/deadline: remove useless param from setup_new_dl_entity References: <1467977331-31116-1-git-send-email-juri.lelli@arm.com> <578328BC.3080504@redhat.com> <20160711100151.69940aff@utopia> To: luca abeni Cc: Juri Lelli , peterz@infradead.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, mingo@redhat.com From: Xunlei Pang Message-ID: <578355D4.9080007@redhat.com> Date: Mon, 11 Jul 2016 16:16:20 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20160711100151.69940aff@utopia> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Mon, 11 Jul 2016 08:16:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/07/11 at 16:01, luca abeni wrote: > Hello, > > On Mon, 11 Jul 2016 13:03:56 +0800 > Xunlei Pang wrote: > >> On 2016/07/08 at 19:28, Juri Lelli wrote: > [...] >>> @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct >>> sched_dl_entity *dl_se, return; >>> >>> /* >>> + * Use the scheduling parameters of the top pi-waiter task, >>> + * if we have one from which we can inherit a deadline. >>> + */ >>> + if (dl_se->dl_boosted && >>> + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) && >>> + dl_prio(pi_task->normal_prio)) >>> + pi_se = &pi_task->dl; >>> + >>> + /* >>> * We use the regular wall clock time to set deadlines in >>> the >>> * future; in fact, we must consider execution overheads >>> (time >>> * spent on hardirq context, etc.). >>> @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq, >>> struct task_struct *p) static void switched_to_dl(struct rq *rq, >>> struct task_struct *p) { >>> if (dl_time_before(p->dl.deadline, rq_clock(rq))) >>> - setup_new_dl_entity(&p->dl, &p->dl); >>> + setup_new_dl_entity(&p->dl); >> I'm curious why we even call setup_new_dl_entity() for non-queued >> cases? It seems more reasonable to do it when it really gets queued. >> We can see that enqueue_task_dl()->update_dl_entity() also has the >> same update logic as switched_to_dl(). > I wondered the same when removing the dl_new field from > sched_dl_entity... But then I realised that enqueue_dl_entity() does > not always invoke update_dl_entity() or replenish_dl_entity()... For > example, when a task switches from SCHED_OTHER (or RT) to -deadline due > to sched_setattr() (or similar) these functions are not invoked. Yeah, but for wake-up cases it does, as ENQUEUE_WAKEUP is set. What I meant is, can we only update for queued tasks in switched_to_dl()? Regards, Xunlei > > > Luca > >> If so, for already queued and boosted cases, rt_mutex_setprio() will >> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity() >> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see >> code: replenish_dl_entity(): >> if (dl_se->dl_deadline == 0) { >> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline; >> dl_se->runtime = pi_se->dl_runtime; >> } >> >> IOW, we don't need to handle !dl boosted cases in >> setup_new_dl_entity(). >> >> Regards, >> Xunlei >> >>> >>> if (task_on_rq_queued(p) && rq->curr != p) { >>> #ifdef CONFIG_SMP