linux-kernel - Re: [PATCH 2/3] sched_ext: Rename scx_bpf_consume() to scx_bpf_dsq_move_to

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Message-ID: <42a6a270d7b01c02eb4d78bb408165641c6b435a@mostlynerdless.de>
Date: Sun, 10 Nov 2024 16:09:15 +0000
From: "Johannes Bechberger" <me@...tlynerdless.de>
To: "Andrea Righi" <arighi@...dia.com>, "Changwoo Min" <multics69@...il.com>
Cc: tj@...nel.org, void@...ifault.com, linux-kernel@...r.kernel.org,
 kernel-team@...a.com, sched-ext@...a.com, ggherdovich@...e.com,
 dschatzberg@...a.com, yougmark94@...il.com, changwoo@...lia.com,
 kernel-dev@...lia.com
Subject: Re: [PATCH 2/3] sched_ext: Rename scx_bpf_consume() to
 scx_bpf_dsq_move_to_local()

Hello all,

the changes look really good and the renaming will make it much easier
to explain what a simple scheduler does, lowering the entry barrier.

> > * Insert @p into the vtime priority queue of the DSQ identified by @dsq_id.
> > - * Tasks queued into the priority queue are ordered by @vtime and always
> > - * consumed after the tasks in the FIFO queue. All other aspects are identical
> > - * to scx_bpf_dsq_insert().
> > + * Tasks queued into the priority queue are ordered by @vtime. All other aspects
> > + * are identical to scx_bpf_dsq_insert().
> >
> > I suggest keeping this part, "and always consumed after the tasks
> > in the FIFO queue." Otherwise, IIRC, there is no place to explain
> > the priority between FIFO and priority DSQs explicitly.
> >
> I think we don't allow anymore to use the FIFO queue and the prio queue
> at the same time. Maybe we should clarify this here and also mention
> that we can't use scx_bpf_dsq_insert_vtime() with the built-in DSQs.
>
> Thanks,
> -Andrea
>

I would like to second that we clarify the differences between the built-in
and the non-builtin DSQs.

Also: Could we mention that the priority queue is stable? If I remember correctly,
then tasks with the same priority are scheduled in a FIFO manner.

Regards
Johannes