Il giorno 2 set 2021, alle ore 15:31, yukuai (C) [off-list ref] ha scritto:

On 2021/08/27 1:00, Paolo Valente wrote:

quoted

Why do you make these extensive changes, while you can leave all the
function unchanged and just modify the above condition to something
like
|| bfqd->num_groups_with_pending_reqs > 1
|| (bfqd->num_groups_with_pending_reqs && bfqd->num_queues_with_pending_reqs_in_root)

Hi, Paolo

I was thinking that if CONFIG_BFQ_GROUP_IOSCHED is enabled, there is no
need to caculate smallest_weight, varied_queue_weights, and
multiple_classes_busy:

If we count root group into num_groups_with_pending_reqs
- If num_groups_with_pending_reqs <= 1, idle is not needed

Unfortunately, if active queues have different weights or belong to
different classes, then idling is needed to preserve per-queue
bandwidths.

Thanks,
Paolo

- If num_groups_with_pending_reqs  > 1, idle is needed

Thus such changes can save some additional overhead.

Thanks
Yu Kuai

quoted

In addition, I still wonder whether you can simply add also the root
group to bfqd->num_groups_with_pending_reqs (when the root group is
active).  This would make the design much cleaner.
Thanks,
Paolo

quoted

-#endif
-		;
+	return varied_queue_weights || multiple_classes_busy;
}

/*
-- 
2.31.1

.