On 2021/08/03 15:07, Paolo Valente wrote:
Il giorno 31 lug 2021, alle ore 09:10, yukuai (C) <yukuai3@xxxxxxxxxx> ha scritto:
On 2021/07/24 15:12, Paolo Valente wrote:
Il giorno 14 lug 2021, alle ore 11:45, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto:
If only one group is activated, specifically
'bfqd->num_groups_with_pending_reqs == 1', there is no need to guarantee
the same share of the throughput of queues in the same group.
Thus change the condition from '> 0' to '> 1' in
bfq_asymmetric_scenario().
I see your point, and I agree with your goal. Yet, your change seems
not to suffer from the following problem.
In addition to the groups that are created explicitly, there is the
implicit root group. So, when bfqd->num_groups_with_pending_reqs ==
1, there may be both active processes in the root group and active
processes in the only group created explicitly. In this case, idling
is needed to preserve service guarantees.
Probably your idea should be improved by making sure that there is
pending I/O only from either the root group or the explicit group.
Thanks,
Paolo
Hi, Paolo
Hi
I'm trying to add support to judge if root group have pending rqs, the
implementation involve setting and clearing the busy state.
I wouldn't use the busy state, as it does not take in-flight requests
into account. For I/O control, the latter are as important as the
ones still queued in the scheduler. For this reason, I take in-flight
requests into account when counting
bfqd->num_groups_with_pending_reqs.
See, e.g., this
if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
...
bfq_weights_tree_remove(bfqd, bfqq);
}
in bfq_completed_request.
I would replicate the same logic in deciding whether the root group
has pending I/O.
Hi, Paolo
Thanks for your advice, I'll send a new patchset soon.
Kuai
