Re: [PATCH v4 14/15] Remove the ext server BW before changing tasks to FAIR

[Joel Fernandes]

On 6/17/2025 4:42 PM, Andrea Righi wrote:
>> +
>> +		/*
>> +		 * We are unloading the sched_ext scheduler, we do not need its
>> +		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
>> +		 * the first SCX task is enqueued (when scx is re-loaded), its DL
>> +		 * server bandwidth will be re-initialized.
>> +		 */
>> +		rq_lock_irqsave(rq, &rf);
>> +		update_rq_clock(rq);
>> +		if (dl_server_active(&rq->ext_server))
>> +			dl_server_stop(&rq->ext_server);
>> +		dl_server_remove_params(&rq->ext_server);
>> +		rq_unlock_irqrestore(rq, &rf);
>> +	}
>> +
>> +
>>  	scx_task_iter_start(&sti);
>>  	while ((p = scx_task_iter_next_locked(&sti))) {
>>  		const struct sched_class *old_class = p->sched_class;
>> @@ -4985,26 +5010,12 @@ static void scx_disable_workfn(struct kthread_work *work)
>>  
>>  	for_each_possible_cpu(cpu) {
>>  		struct rq *rq = cpu_rq(cpu);
>> -		struct rq_flags rf;
>>  
>>  		/*
>>  		 * Invalidate all the rq clocks to prevent getting outdated
>>  		 * rq clocks from a previous scx scheduler.
>>  		 */
>>  		scx_rq_clock_invalidate(rq);
>> -
>> -		/*
>> -		 * We are unloading the sched_ext scheduler, we do not need its
>> -		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
>> -		 * the first SCX task is enqueued (when scx is re-loaded), its DL
>> -		 * server bandwidth will be re-initialized.
>> -		 */
>> -		rq_lock_irqsave(rq, &rf);
>> -		update_rq_clock(rq);
>> -		if (dl_server_active(&rq->ext_server))
>> -			dl_server_stop(&rq->ext_server);
>> -		dl_server_remove_params(&rq->ext_server);
>> -		rq_unlock_irqrestore(rq, &rf);
>>  	}
>
> We should probably remove this for_each_possible_cpu() completely.

Ah right, we only need to call scx_rq_clock_invalidate(rq); per its comment:

+		/*
+		 * Invalidate all the rq clocks to prevent getting outdated
+		 * rq clocks from a previous scx scheduler.
+		 */

So I'll get rid of it and run some tests, thanks!

 - Joel