Re: [RFC PATCH v4 12/28] sched/rt: Implement dl-server operations for rt-cgroups.

[Juri Lelli]

Hello,

On 01/12/25 13:41, Yuri Andriaccio wrote:
> - Implement rt_server_pick, the callback that deadline servers use to
>   pick a task to schedule.
>   - rt_server_pick(): pick the next runnable rt task and tell the
>     scheduler that it is going to be scheduled next.
> 
> - Let enqueue/dequeue_task_rt function start/stop the attached deadline
>   server when the first/last task is enqueued/dequeued on a specific
>   rq/server.
> 
> - Change update_curr_rt to perform a deadline server update if the
>   updated task is served by non-root group.
> 
> - Update inc/dec_dl_tasks to account the number of active tasks in the
>   local runqueue for rt-cgroups servers, as their local runqueue is
>   different from the global runqueue, and thus when a rt-group server is
>   activated/deactivated, the number of served tasks' must be
>   added/removed. This uses nr_running to be compatible with future
>   dl-server interfaces.
> 
> - Update inc/dec_rt_prio_smp to change a rq's cpupri only if the rt_rq
>   is the global runqueue, since cgroups are scheduled via their
>   dl-server priority.
> 
> - Update inc/dec_rt_tasks to account for waking/sleeping tasks on the
>   global runqueue, when the task runs on the root cgroup, or its local
>   dl server is active. The accounting is not done when servers are
>   throttled, as they will add/sub the number of tasks running when they
>   get enqueued/dequeued. For rt cgroups, account for the number of active
>   tasks in the nr_running field of the local runqueue
>   (add/sub_nr_running), as this number is used when a dl server is
>   enqueued/dequeued.
> 
> - Update set_task_rq to record the dl_rq, tracking which deadline
>   server manages a task.
> 
> - Update set_task_rq to not use the parent field anymore, as it is
>   unused by this patchset's code. Remove the unused parent field from
>   sched_rt_entity.
> 
> Co-developed-by: Alessio Balsini <a.balsini@xxxxxxxx>
> Signed-off-by: Alessio Balsini <a.balsini@xxxxxxxx>
> Co-developed-by: Andrea Parri <parri.andrea@xxxxxxxxx>
> Signed-off-by: Andrea Parri <parri.andrea@xxxxxxxxx>
> Co-developed-by: luca abeni <luca.abeni@xxxxxxxxxxxxxxx>
> Signed-off-by: luca abeni <luca.abeni@xxxxxxxxxxxxxxx>
> Signed-off-by: Yuri Andriaccio <yurand2000@xxxxxxxxx>
> ---

...

>  /*
> @@ -725,6 +769,14 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
>  	check_schedstat_required();
>  	update_stats_wait_start_rt(rt_rq_of_se(rt_se), rt_se);
> 
> +	/* Task arriving in an idle group of tasks. */
> +	if (IS_ENABLED(CONFIG_RT_GROUP_SCHED) &&
                         ^^^
Shall we be using rt_group_sched_enabled() here and elsewhere instead?

Thanks,
Juri