linux-kernel - Re: [PATCH sched_ext/for-6.11] sched_ext: Documentation: Remove mentions of scx_bpf_switch

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Date: Tue, 02 Jul 2024 14:10:36 +0530
From: Aboorva Devarajan <aboorvad@...ux.ibm.com>
To: Tejun Heo <tj@...nel.org>
Cc: void@...ifault.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH sched_ext/for-6.11] sched_ext: Documentation: Remove
 mentions of scx_bpf_switch_all

On Mon, 2024-07-01 at 07:53 -1000, Tejun Heo wrote:
> Hello,
> 
> On Mon, Jul 01, 2024 at 06:00:22PM +0530, Aboorva Devarajan wrote:
> ...
> > +sched_ext is used only when the BPF scheduler is loaded and
> > running. To use
> > +sched_ext, a task can invoke ``sched_setscheduler`` with the
> > ``SCHED_EXT``
> > +policy constant.
> 
> I wonder whether the last sentence is a bit confusing given that
> tasks can
> be on SCX without setting SCHED_EXT.
> 
> > +When the BPF scheduler is not loaded, tasks with the
> > ``SCHED_EXT`` policy are
> > +treated as ``SCHED_NORMAL`` and scheduled by CFS.
> > ``SCHED_NORMAL`` tasks
> > +continue to be scheduled by CFS.
> > +
> > +When the BPF scheduler is loaded, all tasks with the
> > ``SCHED_EXT`` policy are
> > +switched to sched_ext. By default, if the ``struct ops->flag`` is
> > not set to
> > +``SCX_OPS_SWITCH_PARTIAL``, ``SCHED_EXT``, ``SCHED_NORMAL``, and
> > lower class
> > +tasks are scheduled by sched_ext. In this case, all
> > ``SCHED_NORMAL``,
> > +``SCHED_BATCH``, ``SCHED_IDLE``, and ``SCHED_EXT`` tasks are
> > scheduled by
> > +sched_ext.
> 
> How about something like:
> 
> When the BPF scheduler is loaded and ``SCX_OPS_SWITCH_PARTIAL`` is
> not set
> in ops->flags, all ``SCHED_NORMAL``, ``SCHED_BATCH``,
> ``SCHED_IDLE``, and
> ``SCHED_EXT`` tasks are scheduled by sched_ext.
> 
> > +However, if the ``struct ops->flag`` is set
> > to``SCX_OPS_SWITCH_PARTIAL``,
> > +only tasks with the policy set to ``SCHED_EXT`` are scheduled by
> > sched_ext.
> 
> And update this paragraph in a similar fashion?
> 
> Thanks.
> 

Hi Tejun, Thanks for the review.

Sent out a v2 with the suggested changes.