linux-kernel - Re: [PATCH v3] sched_ext: Implement SCX_OPS_TRACK

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Message-ID: <aFmWGi8n1ndB1K_M@slm.duckdns.org>
Date: Mon, 23 Jun 2025 07:59:54 -1000
From: Tejun Heo <tj@...nel.org>
To: Henry Huang <henry.hj@...group.com>
Cc: changwoo@...lia.com, arighi@...dia.com, void@...ifault.com,
	谈鉴锋 <henry.tjf@...group.com>,
	"Yan Yan(cailing)" <yanyan.yan@...group.com>,
	linux-kernel@...r.kernel.org, sched-ext@...ts.linux.dev
Subject: Re: [PATCH v3] sched_ext: Implement SCX_OPS_TRACK_MIGRATION

Hello,

On Mon, Jun 23, 2025 at 02:30:33PM +0800, Henry Huang wrote:
> For some BPF-schedulers, they should do something when
> task is doing migration, such as updating per-cpu map.
> If SCX_OPS_TRACK_MIGRATION is set, runnable/quiescent
> would be called whether task is doing migration or not.

It's rather odd to invoke runnable/quiescent on these transitions as the
runnable state isn't actually changing and the events end up triggering for
all the migration operations that SCX does internally.

In the head message (BTW, if it's just a single patch, it'd be better to
include all the context in the patch description), you said that this is
needed to udpate percpu data structures when tasks migrate. Wouldn't you be
able to do that by tracking whether the current CPU is different from the
previous one from ops.running()?

Thanks.

-- 
tejun