linux-kernel - Re: [PATCHSET sched_ext/for-6.13] sched_ext: Rename dispatch and consume kfuncs

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Message-ID: <ZzCc3h7RN4T-NKv9@gpd3>
Date: Sun, 10 Nov 2024 12:45:34 +0100
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>
Cc: void@...ifault.com, linux-kernel@...r.kernel.org, kernel-team@...a.com,
	sched-ext@...a.com, multics69@...il.com, me@...tlynerdless.de,
	ggherdovich@...e.com, dschatzberg@...a.com, yougmark94@...il.com
Subject: Re: [PATCHSET sched_ext/for-6.13] sched_ext: Rename dispatch and
 consume kfuncs

Hi Tejun,

On Sat, Nov 09, 2024 at 09:48:29AM -1000, Tejun Heo wrote:
> In sched_ext API, a repeatedly reported pain point is the overuse of the
> verb "dispatch" and confusion around "consume":
> 
> - ops.dispatch()
> - scx_bpf_dispatch[_vtime]()
> - scx_bpf_consume()
> - scx_bpf_dispatch[_vtime]_from_dsq*()
> 
> This overloading of the term is historical. Originally, there were only
> built-in DSQs and moving a task into a DSQ always dispatched it for
> execution. Using the verb "dispatch" for the kfuncs to move tasks into these
> DSQs made sense.
> 
> Later, user DSQs were added and scx_bpf_dispatch[_vtime]() updated to be
> able to insert tasks into any DSQ. The only allowed DSQ to DSQ transfer was
> from a non-local DSQ to a local DSQ and this operation was named "consume".
> This was already confusing as a task could be dispatched to a user DSQ from
> ops.enqueue() and then the DSQ would have to be consumed in ops.dispatch().
> Later addition of scx_bpf_dispatch_from_dsq*() made the confusion even worse
> as "dispatch" in this context meant moving a task to an arbitrary DSQ from a
> user DSQ.
> 
> Clean up the API with the following renames:
> 
> 1. scx_bpf_dispatch[_vtime]()           -> scx_bpf_dsq_insert[_vtime]()
> 2. scx_bpf_consume()                    -> scx_bpf_dsq_move_to_local()
> 3. scx_bpf_dispatch[_vtime]_from_dsq*() -> scx_bpf_dsq_move[_vtime]*()
> 
> This patchset is on top of sched_ext/for-6.13 72b85bf6a7f6 ("sched_ext:
> scx_bpf_dispatch_from_dsq_set_*() are allowed from unlocked context") and
> contains the following patches:
> 
>  0001-sched_ext-Rename-scx_bpf_dispatch-_vtime-to-scx_bpf_.patch
>  0002-sched_ext-Rename-scx_bpf_consume-to-scx_bpf_dsq_move.patch
>  0003-sched_ext-Rename-scx_bpf_dispatch-_vtime-_from_dsq-s.patch
> 
> and is always available in the following git branch:
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-api-rename-dispatch
> 
> diffstat follows. Thanks.
> 
>  kernel/sched/ext.c                       |  238 +++++++++++++++++++++++++++++++++--------------------
>  tools/sched_ext/include/scx/common.bpf.h |   18 ++--
>  tools/sched_ext/include/scx/compat.bpf.h |  117 +++++++++++++++++++++++---
>  tools/sched_ext/scx_central.bpf.c        |   14 +--
>  tools/sched_ext/scx_flatcg.bpf.c         |   20 ++--
>  tools/sched_ext/scx_qmap.bpf.c           |   36 ++++----
>  tools/sched_ext/scx_simple.bpf.c         |   16 +--
>  7 files changed, 308 insertions(+), 151 deletions(-)

Overall it looks good to me, we should probably update also
Documentation/scheduler/sched-ext.rst.

Thanks,
-Andrea