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

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Message-ID: <ZzCej_1NNr2wB0AD@gpd3>
Date: Sun, 10 Nov 2024 12:52:47 +0100
From: Andrea Righi <arighi@...dia.com>
To: 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, me@...tlynerdless.de,
	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()

On Sun, Nov 10, 2024 at 07:03:03PM +0900, Changwoo Min wrote:
> Hello Tejun,
> 
> Overall looks good to me. I have one minior comment:
> 
> On 24. 11. 10. 04:48, Tejun Heo wrote:
> > @@ -6372,9 +6372,8 @@ __bpf_kfunc void scx_bpf_dispatch(struct task_struct *p, u64 dsq_id, u64 slice,
> >    * @enq_flags: SCX_ENQ_*
> >    *
> >    * 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