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Message-ID: <76d535f6-f92c-4564-aafa-290042cf76a9@gmail.com>
Date: Wed, 29 Nov 2023 16:53:35 +0800
From: Benjamin Tang <tangsong8264@...il.com>
To: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
linux-kernel@...r.kernel.org,
Benjamin Tang <tangsong8264@...il.com>
Subject: [RFC] Core Scheduling unnecessary force idle?
When I'm reading the code related to "core scheduling", I have a question.
Say the RQs in a particular core look like this:
Let CFS1 and CFS4 be 2 untagged CFS tasks.
Let CFS2 and CFS3 be 2 untagged CFS tasks.
rq0 rq1
CFS1(no tag) CFS3(tagged)
CFS2(tagged) CFS4(no tag)
Say schedule() runs on rq0. In the core-wide pick logic, if I'm not
mistaken,
the end result of the selection will be (say prio(CFS1) > prio(CFS3)):
rq0 rq1
CFS1(no tag) IDLE
Why not consider trying to find untagged tasks for rq1 here?
Is it because it seems less fair, or are there other considerations?
I would be very grateful if someone could give me some suggestions.
Thanks!
Best Wishes
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