From: Vincent Guittot <vincent.guittot@linaro.org>
To: Qais Yousef <qais.yousef@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] sched: rt: Make RT capacity aware
Date: Tue, 29 Oct 2019 13:54:24 +0100 [thread overview]
Message-ID: <CAKfTPtDnt6oh7X6dGnPUn70sLJXAQoxdkn0GCwdPvA8G4Wg0fA@mail.gmail.com> (raw)
In-Reply-To: <20191029124630.ivfbpenue3fw33qt@e107158-lin.cambridge.arm.com>
On Tue, 29 Oct 2019 at 13:46, Qais Yousef <qais.yousef@arm.com> wrote:
>
> On 10/29/19 13:20, Vincent Guittot wrote:
> > > > Making big cores the default CPUs for all RT tasks is not a minor
> > > > change and IMO locality should stay the default behavior when there is
> > > > no uclamp constraint
> > >
> > > How this is affecting locality? The task will always go to the big core, so it
> > > should be local.
> >
> > local with the waker
> > You will force rt task to run on big cluster although waker, data and
> > interrupts can be on little one.
> > So making big core as default is far from always being the best choice
>
> This is loaded with assumptions IMO. AFAICT we don't know what's the best
> choice.
>
> First, the value of uclamp.min is outside of the scope of this patch. Unless
> what you're saying is that when uclamp.min is 1024 then we should NOT choose a
> big cpu then there's no disagreement about what this patch do. If that's what
> you're objecting to please be more specific about how do you see this working
> instead.
My point is that this patch makes the big cores the default CPUs for
RT tasks which is far from being a minor change and far from being an
obvious default good choice
>
> If your objection is purely based on the choice of uclamp.min then while
> I agree that on modern systems the little cores are good enough for the
> majority of RT tasks in average Android systems. But I don't feel confident to
> reach this conclusion on low end systems where the little core doesn't have
> enough grunt in many cases. So I see the current default is adequate and the
> responsibility of further tweaking lies within the hands of the system admin.
>
> --
> Qais Yousef
next prev parent reply other threads:[~2019-10-29 12:54 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 [this message]
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
2020-02-05 14:48 ` Qais Yousef
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