From: Valentin Schneider <valentin.schneider@arm.com>
To: Steven Rostedt <rostedt@goodmis.org>, Qais Yousef <qais.yousef@arm.com>
Cc: Pavan Kondeti <pkondeti@codeaurora.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] sched: rt: Make RT capacity aware
Date: Mon, 3 Feb 2020 17:15:01 +0000 [thread overview]
Message-ID: <8868c5cf-e3f4-04e1-e071-0476ac813191@arm.com> (raw)
In-Reply-To: <20200203111451.0d1da58f@oasis.local.home>
On 03/02/2020 16:14, Steven Rostedt wrote:
> On Mon, 3 Feb 2020 14:27:14 +0000
> Qais Yousef <qais.yousef@arm.com> wrote:
>
>> I don't see one right answer here. The current mechanism could certainly do
>> better; but it's not clear what better means without delving into system
>> specific details. I am open to any suggestions to improve it.
>
> The way I see this is that if there's no big cores available but little
> cores are, and the RT task has those cores in its affinity mask then
> the task most definitely should consider moving to the little core. The
> cpu_find() should return them!
>
> But, what we can do is to mark the little core that's running an RT
> task on a it that prefers bigger cores, as "rt-overloaded". This will
> add this core into the being looked at when another core schedules out
> an RT task. When that happens, the RT task on the little core will get
> pulled back to the big core.
>
That sounds sensible enough - it's also very similar to what we have for
CFS, labeled under "misfit tasks" (i.e. tasks that are "too big" for
LITTLEs).
>
> Note, this will require a bit more logic as the overloaded code wasn't
> designed for migration of running tasks, but that could be added.
>
I haven't adventured too much within RT land, but FWIW that's what we use
the CPU stopper for in CFS (see active_load_balance_cpu_stop()).
> -- Steve
>
next prev parent reply other threads:[~2020-02-03 17:15 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 10:46 [PATCH v2] sched: rt: Make RT capacity aware Qais Yousef
2019-10-23 12:34 ` Qais Yousef
2019-10-28 14:37 ` Peter Zijlstra
2019-10-28 18:01 ` Steven Rostedt
2019-10-28 20:50 ` Peter Zijlstra
2019-12-20 16:01 ` Qais Yousef
2019-12-20 17:18 ` Peter Zijlstra
2019-12-20 17:36 ` Qais Yousef
2019-11-07 9:15 ` Qais Yousef
2019-11-18 15:43 ` Qais Yousef
2019-11-18 15:53 ` Steven Rostedt
2019-11-18 16:12 ` Qais Yousef
2019-10-29 8:13 ` Vincent Guittot
2019-10-29 11:02 ` Qais Yousef
2019-10-29 11:17 ` Vincent Guittot
2019-10-29 11:48 ` Qais Yousef
2019-10-29 12:20 ` Vincent Guittot
2019-10-29 12:46 ` Qais Yousef
2019-10-29 12:54 ` Vincent Guittot
2019-10-29 13:02 ` Peter Zijlstra
2019-10-29 20:36 ` Patrick Bellasi
2019-10-30 8:04 ` Vincent Guittot
2019-10-30 9:26 ` Qais Yousef
2019-10-30 12:11 ` Quentin Perret
2019-10-30 11:57 ` Dietmar Eggemann
2019-10-30 17:43 ` Qais Yousef
2019-11-28 13:59 ` Dietmar Eggemann
2019-11-25 21:36 ` Steven Rostedt
2019-11-26 9:39 ` Qais Yousef
2019-12-25 10:38 ` [tip: sched/core] sched/rt: Make RT capacity-aware tip-bot2 for Qais Yousef
2020-01-31 10:06 ` [PATCH v2] sched: rt: Make RT capacity aware Pavan Kondeti
2020-01-31 15:34 ` Qais Yousef
[not found] ` <CAEU1=PnYryM26F-tNAT0JVUoFcygRgE374JiBeJPQeTEoZpANg@mail.gmail.com>
2020-02-03 5:32 ` Pavan Kondeti
2020-02-03 14:57 ` Qais Yousef
2020-02-03 14:27 ` Qais Yousef
2020-02-03 16:14 ` Steven Rostedt
2020-02-03 17:15 ` Valentin Schneider [this message]
2020-02-03 17:17 ` Qais Yousef
2020-02-03 18:12 ` Steven Rostedt
2020-02-03 19:03 ` Qais Yousef
2020-02-04 17:23 ` Dietmar Eggemann
2020-02-05 14:48 ` Qais Yousef
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