linux-kernel - Re: [PATCH v3 2/5] sched_ext: Manage the validity of scx_rq

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Message-ID: <Z1CjiYdeYMzxZNuo@slm.duckdns.org>
Date: Wed, 4 Dec 2024 08:46:33 -1000
From: Tejun Heo <tj@...nel.org>
To: Changwoo Min <changwoo@...lia.com>
Cc: Changwoo Min <multics69@...il.com>, void@...ifault.com,
	mingo@...hat.com, peterz@...radead.org, kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/5] sched_ext: Manage the validity of scx_rq_clock

Hello,

On Wed, Dec 04, 2024 at 10:42:13AM +0900, Changwoo Min wrote:
> I investigated all sched_ext_ops. Besides these two ops, all the
> rest are control operations, of which BPF operation should be
> relatively simple. On the other hand, ops.running() and
> ops.update_idle() are different from the others since a CPU
> executes a task or becomes idle, which could be arbitrarily long.
> So I think refreshing the clock in those cases would be nice.
> Does it make sense to you?

Hmm... I'm not really following. Both ops.running() and ops.update_idle()
are called during task switches with rq lock held. I don't see why they'd be
any different in terms of expected runtime, which should be pretty short,
compared to any other rq-locked operations.

Thanks.

-- 
tejun