From: Valentin Schneider <valentin.schneider@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Scott Wood <swood@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Rik van Riel <riel@surriel.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: [RFC PATCH 0/3] newidle_balance() latency mitigation
Date: Thu, 30 Apr 2020 14:56:29 +0100 [thread overview]
Message-ID: <jhjwo5xcc1e.mognet@arm.com> (raw)
In-Reply-To: <CAKfTPtA_duZpnvMx+czAosCikVL=cESKhPQcRrQUdKWKobZBaA@mail.gmail.com>
On 30/04/20 13:42, Vincent Guittot wrote:
>> >> Random thought that just occurred to me; in the grand scheme of things,
>> >> with something in the same spirit as task-stealing (i.e. don't bother with
>> >> a full fledged balance at newidle, just pick one spare task somewhere),
>> >> none of this would be required.
>> >
>> > newly idle load balance already stops after picking 1 task
>>
>> Mph, I had already forgotten your changes there. Is that really always the
>> case for newidle? In e.g. the busiest->group_type == group_fully_busy case,
>> I think we can pull more than one task.
>
> for newly_idle load balance, detach_tasks stops after finding 1 suitable task
>
Right, I hadn't noticed
7e96fa5875d4 ("sched: pull only one task during NEWIDLE balancing to limit critical section")
>>
>> > Now if your proposal is to pick one random task on one random cpu, I'm
>> > clearly not sure that's a good idea
>> >
>>
>> IIRC Steve's implementation was to "simply" pull one task from any CPU
>> within the LLC domain that had > 1 runnable tasks. I quite like this since
>> picking any one task is almost always better than switching to the idle
>> task, but it wasn't a complete newidle_balance() replacement just yet.
>>
>> >
>> >>
>> >> Sadly I don't think anyone has been looking at it any recently.
next prev parent reply other threads:[~2020-04-30 13:56 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 5:02 [RFC PATCH 0/3] newidle_balance() latency mitigation Scott Wood
2020-04-28 5:02 ` [RFC PATCH 1/3] sched/fair: Call newidle_balance() from finish_task_switch() Scott Wood
2020-04-28 21:37 ` Valentin Schneider
2020-04-28 22:09 ` Peter Zijlstra
2020-04-28 22:55 ` Scott Wood
2020-04-28 23:02 ` Peter Zijlstra
2020-04-28 23:20 ` Scott Wood
2020-04-29 9:05 ` Peter Zijlstra
2020-04-30 1:31 ` Scott Wood
2020-05-11 10:58 ` Peter Zijlstra
2020-05-11 12:13 ` Peter Zijlstra
2020-04-28 22:33 ` Scott Wood
2020-04-29 12:00 ` Valentin Schneider
2020-04-29 8:27 ` Vincent Guittot
2020-04-30 1:36 ` Scott Wood
2020-04-28 5:02 ` [RFC PATCH 2/3] sched/fair: Enable interrupts when dropping lock in newidle_balance() Scott Wood
2020-04-28 5:02 ` [RFC PATCH 3/3] sched,rt: break out of load balancing if an RT task appears Scott Wood
2020-04-28 21:56 ` Valentin Schneider
2020-04-28 22:33 ` Scott Wood
2020-04-28 22:52 ` Scott Wood
2020-04-29 12:01 ` Valentin Schneider
2020-04-28 13:27 ` [RFC PATCH 0/3] newidle_balance() latency mitigation Steven Rostedt
2020-04-29 23:13 ` Valentin Schneider
2020-04-30 7:44 ` Vincent Guittot
2020-04-30 10:14 ` Valentin Schneider
2020-04-30 12:42 ` Vincent Guittot
2020-04-30 13:56 ` Valentin Schneider [this message]
2020-04-30 12:48 ` Vincent Guittot
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