From: Quentin Perret <qperret@google.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Patrick Bellasi <patrick.bellasi@matbug.net>,
Qais Yousef <qais.yousef@arm.com>, 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: Wed, 30 Oct 2019 12:11:01 +0000 [thread overview]
Message-ID: <20191030121101.GA172224@google.com> (raw)
In-Reply-To: <CAKfTPtDFLsn-uSV2ms1qPMMs+2GYWK2jYw8=-2pr_BpBRid6Kw@mail.gmail.com>
On Wednesday 30 Oct 2019 at 09:04:44 (+0100), Vincent Guittot wrote:
> That's the point of my comment, choosing big cores as default and
> always best choice is far from being obvious.
> And this patch changes the default behavior without study of the
> impact apart from stating that this should be ok
The current behaviour is totally bogus on big.LITTLE TBH, and nobody
uses it as-is. Vendors hack RT a lot for that exact reason.
Right now a RT task gets a random CPU, which on big.LITTLE is
effectively equivalent to selecting a random OPP on SMP. And since RT is
all about predicatbility, I'd argue sticking to the big CPUs for
consistency with the frequency selection policy is the only sensible
default.
So +1 from me for Qais' patch :)
Thanks,
Quentin
next prev parent reply other threads:[~2019-10-30 12:11 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 [this message]
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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