From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Qais Yousef <qais.yousef@arm.com>, Steven Rostedt <rostedt@goodmis.org>
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>,
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: Tue, 4 Feb 2020 18:23:15 +0100 [thread overview]
Message-ID: <c30eddd3-143e-03f1-6975-97f5af1d3075@arm.com> (raw)
In-Reply-To: <20200203190259.bnly7hfp3wfiteof@e107158-lin>
On 03/02/2020 20:03, Qais Yousef wrote:
> On 02/03/20 13:12, Steven Rostedt wrote:
>> On Mon, 3 Feb 2020 17:17:46 +0000
>> Qais Yousef <qais.yousef@arm.com> wrote:
[...]
> In the light of strictly adhering to priority based scheduling; yes this makes
> sense. Though I still think the migration will produce worse performance, but
> I can appreciate even if that was true it breaks the strict priority rule.
>
>>
>> You can add to the logic that you do not take over an RT task that is
>> pinned and can't move itself. Perhaps that may be the only change to
>
> I get this.
>
>> cpu_find(), is that it will only pick a big CPU if little CPUs are
>> available if the big CPU doesn't have a pinned RT task on it.
>
> But not that. Do you mind rephrasing it?
>
> Or let me try first:
>
> 1. Search all priority levels for a fitting CPU
Just so I get this right: All _lower_ prio levels than p->prio, right?
> 2. If failed, return the first lowest mask found
> 3. If it succeeds, remove any CPU that has a pinned task in it
> 4. If the lowest_mask is empty, return (2).
> 5. Else return the lowest_mask with the fitting CPU(s)
Mapping this to the 5 FIFO tasks rt-tasks of Pavan's example (all
p->prio=89 (dflt rt-app prio), dflt min_cap=1024 max_cap=1024) on a 4
big (Cpu Capacity=1024) 4 little (Cpu capacity < 1024) system:
You search from idx 1 to 11 [p->prio=89 eq. idx (task_pri)=12] and since
there are no lower prior RT tasks the lowest mask of idx=1 (CFS or Idle)
for the 5th RT task is returned.
But that means that CPU capacity trumps priority?
[...]
next prev parent reply other threads:[~2020-02-04 17:23 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
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 [this message]
2020-02-05 14:48 ` Qais Yousef
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