From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org,
Luca Abeni <luca.abeni@santannapisa.it>,
Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>,
Thomas Gleixner <tglx@linutronix.de>,
Joel Fernandes <joel@joelfernandes.org>,
Vineeth Pillai <vineeth@bitbyteword.org>,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [RFC PATCH V3 6/6] sched/fair: Implement starvation monitor
Date: Fri, 16 Jun 2023 13:51:49 +0200 [thread overview]
Message-ID: <20230616115149.GK83892@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <bd9977efff8cc3e002c4b2db02f611167905a99f.1686239016.git.bristot@kernel.org>
On Thu, Jun 08, 2023 at 05:58:18PM +0200, Daniel Bristot de Oliveira wrote:
> From: Juri Lelli <juri.lelli@redhat.com>
>
> Starting deadline server for lower priority classes right away when
> first task is enqueued might break guarantees, as tasks belonging to
> intermediate priority classes could be uselessly preempted. E.g., a well
> behaving (non hog) FIFO task can be preempted by NORMAL tasks even if
> there are still CPU cycles available for NORMAL tasks to run, as they'll
> be running inside the fair deadline server for some period of time.
>
> To prevent this issue, implement a starvation monitor mechanism that
Why should this be prevented? FIFO can be preempted by a higher
priority FIFO/RR, or in this case by DEADLINE, and always by stop_task.
Just accept this.
Anything that's build around FIFO-99 not getting preempted is just plain
broken. Don't try and pander to broken.
next prev parent reply other threads:[~2023-06-16 11:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-08 15:58 [RFC PATCH V3 0/6] SCHED_DEADLINE server infrastructure Daniel Bristot de Oliveira
2023-06-08 15:58 ` [RFC PATCH V3 1/6] sched: Unify runtime accounting across classes Daniel Bristot de Oliveira
2023-06-13 13:24 ` Phil Auld
2023-06-16 14:30 ` Valentin Schneider
2023-06-08 15:58 ` [RFC PATCH V3 2/6] sched/deadline: Collect sched_dl_entity initialization Daniel Bristot de Oliveira
2023-06-13 13:25 ` Phil Auld
2023-06-16 14:31 ` Valentin Schneider
2023-06-08 15:58 ` [RFC PATCH V3 3/6] sched/deadline: Move bandwidth accounting into {en,de}queue_dl_entity Daniel Bristot de Oliveira
2023-06-16 14:31 ` Valentin Schneider
2023-06-08 15:58 ` [RFC PATCH V3 4/6] sched/deadline: Introduce deadline servers Daniel Bristot de Oliveira
2023-06-13 13:21 ` Phil Auld
2023-06-23 16:47 ` Valentin Schneider
2023-07-04 15:52 ` Daniel Bristot de Oliveira
2023-07-04 17:25 ` Joel Fernandes
2023-07-04 17:28 ` Joel Fernandes
2023-06-08 15:58 ` [RFC PATCH V3 5/6] sched/fair: Add trivial fair server Daniel Bristot de Oliveira
2023-06-16 12:59 ` Peter Zijlstra
2023-06-16 13:00 ` Daniel Bristot de Oliveira
2023-06-16 13:12 ` Peter Zijlstra
2023-06-16 13:18 ` Daniel Bristot de Oliveira
2023-06-08 15:58 ` [RFC PATCH V3 6/6] sched/fair: Implement starvation monitor Daniel Bristot de Oliveira
2023-06-12 1:57 ` Joel Fernandes
2023-06-12 14:45 ` Daniel Bristot de Oliveira
2023-06-12 20:35 ` Joel Fernandes
2023-06-13 13:41 ` Daniel Bristot de Oliveira
2023-06-13 15:32 ` Joel Fernandes
2023-06-14 13:45 ` Daniel Bristot de Oliveira
2023-06-14 14:15 ` Juri Lelli
2023-06-14 18:27 ` Joel Fernandes
2023-06-14 18:24 ` Joel Fernandes
2023-06-16 12:05 ` Peter Zijlstra
2023-06-16 12:48 ` Daniel Bristot de Oliveira
2023-06-19 12:02 ` Peter Zijlstra
2023-06-19 14:58 ` Daniel Bristot de Oliveira
2023-06-16 11:56 ` Peter Zijlstra
2023-06-16 11:51 ` Peter Zijlstra [this message]
2023-06-16 13:27 ` Daniel Bristot de Oliveira
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