Re: [RFC PATCH 2/7] sched/fair: Handle throttle path for task based throttle

[Chengming Zhou]

On 2025/3/13 15:21, Aaron Lu wrote:
> From: Valentin Schneider <vschneid@xxxxxxxxxx>
>
> Once a cfs_rq gets throttled, for all tasks belonging to this cfs_rq,
> add a task work to them so that when those tasks return to user, the
> actual throttle/dequeue can happen.
>
> Note that since the throttle/dequeue always happens on a task basis when
> it returns to user, it's no longer necessary for check_cfs_rq_runtime()
> to return a value and pick_task_fair() acts differently according to that
> return value, so check_cfs_rq_runtime() is changed to not return a
> value.

Previously with the per-cfs_rq throttling, we use update_curr() -> put() path
to throttle the cfs_rq and dequeue it from the cfs_rq tree.

Now with your per-task throttling, maybe things can become simpler. That we
can just throttle_cfs_rq() (cfs_rq subtree) when curr accouting to mark these
throttled.

Then then if we pick a task from a throttled cfs_rq subtree, we can setup task work
for it, so we don't botter with the delayed_dequeue task case that Prateek mentioned.

WDYT?

Thanks.