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Thu, 08 Aug 2019 02:45:49 -0700 (PDT) Received: from localhost.localdomain ([151.29.237.107]) by smtp.gmail.com with ESMTPSA id c15sm20285767wrb.80.2019.08.08.02.45.48 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 08 Aug 2019 02:45:49 -0700 (PDT) Date: Thu, 8 Aug 2019 11:45:46 +0200 From: Juri Lelli To: Dietmar Eggemann Cc: Peter Zijlstra , mingo@kernel.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, bristot@redhat.com, balsini@android.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, rostedt@goodmis.org Subject: Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers Message-ID: <20190808094546.GJ29310@localhost.localdomain> References: <20190726145409.947503076@infradead.org> <20190726161358.056107990@infradead.org> <34710762-f813-3913-0e55-fde7c91c6c2d@arm.com> <20190808075635.GB17205@worktop.programming.kicks-ass.net> <20cc05d3-0d0f-a558-2bbe-3b72527dd9bc@arm.com> <20190808084652.GG29310@localhost.localdomain> <99a8339d-8e06-bff8-284b-1829d0683a7a@arm.com> <20190808092744.GI29310@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190808092744.GI29310@localhost.localdomain> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/08/19 11:27, Juri Lelli wrote: > On 08/08/19 10:57, Dietmar Eggemann wrote: > > On 8/8/19 10:46 AM, Juri Lelli wrote: > > > On 08/08/19 10:11, Dietmar Eggemann wrote: > > >> On 8/8/19 9:56 AM, Peter Zijlstra wrote: > > >>> On Wed, Aug 07, 2019 at 06:31:59PM +0200, Dietmar Eggemann wrote: > > >>>> On 7/26/19 4:54 PM, Peter Zijlstra wrote: > > >>>>> > > >>>>> > > >>>>> Signed-off-by: Peter Zijlstra (Intel) > > >>>> > > >>>> [...] > > >>>> > > >>>>> @@ -889,6 +891,8 @@ static void update_curr(struct cfs_rq *c > > >>>>> trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); > > >>>>> cgroup_account_cputime(curtask, delta_exec); > > >>>>> account_group_exec_runtime(curtask, delta_exec); > > >>>>> + if (curtask->server) > > >>>>> + dl_server_update(curtask->server, delta_exec); > > >>>>> } > > >>>> > > >>>> I get a lockdep_assert_held(&rq->lock) related warning in start_dl_timer() > > >>>> when running the full stack. > > >>> > > >>> That would seem to imply a stale curtask->server value; the hunk below: > > >>> > > >>> --- a/kernel/sched/core.c > > >>> +++ b/kernel/sched/core.c > > >>> @@ -3756,8 +3756,11 @@ pick_next_task(struct rq *rq, struct tas > > >>> > > >>> for_each_class(class) { > > >>> p = class->pick_next_task(rq, NULL, NULL); > > >>> - if (p) > > >>> + if (p) { > > >>> + if (p->sched_class == class && p->server) > > >>> + p->server = NULL; > > >>> return p; > > >>> + } > > >>> } > > >>> > > >>> > > >>> Was supposed to clear p->server, but clearly something is going 'funny'. > > >> > > >> What about the fast path in pick_next_task()? > > >> > > >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > >> index bffe849b5a42..f1ea6ae16052 100644 > > >> --- a/kernel/sched/core.c > > >> +++ b/kernel/sched/core.c > > >> @@ -3742,6 +3742,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > > >> if (unlikely(!p)) > > >> p = idle_sched_class.pick_next_task(rq, prev, rf); > > >> > > >> + if (p->sched_class == &fair_sched_class && p->server) > > >> + p->server = NULL; > > >> + > > > > > > Hummm, but then who sets it back to the correct server. AFAIU > > > update_curr() needs a ->server to do the correct DL accounting? > > > > Ah, OK, this would kill the whole functionality ;-) > > > > I'm thinking we could use &rq->fair_server. It seems to pass the point > we are discussing about, but then virt box becomes unresponsive (busy > loops). I'd like to take this last sentence back, I was able to run a few boot + hackbench + shutdown cycles with the following applied (guess too much debug printks around before). --->8--- kernel/sched/deadline.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 3fe82b8f7825..d4a20072d4c0 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1312,6 +1312,10 @@ void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec) void dl_server_start(struct sched_dl_entity *dl_se) { + if (!dl_server(dl_se)) { + dl_se->dl_server = 1; + setup_new_dl_entity(dl_se); + } enqueue_dl_entity(dl_se, dl_se, ENQUEUE_WAKEUP); } @@ -1324,12 +1328,9 @@ void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq, dl_server_has_tasks_f has_tasks, dl_server_pick_f pick) { - dl_se->dl_server = 1; dl_se->rq = rq; dl_se->server_has_tasks = has_tasks; dl_se->server_pick = pick; - - setup_new_dl_entity(dl_se); } /* @@ -2829,6 +2830,7 @@ static void __dl_clear_params(struct sched_dl_entity *dl_se) dl_se->dl_yielded = 0; dl_se->dl_non_contending = 0; dl_se->dl_overrun = 0; + dl_se->dl_server = 0; } void init_dl_entity(struct sched_dl_entity *dl_se) --->8--- kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7a161472decd..355cb1382aef 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3783,6 +3783,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) if (unlikely(!p)) p = idle_sched_class.pick_next_task(rq, prev, rf); + if (p->sched_class == &fair_sched_class) + p->server = &rq->fair_server; + return p; }