Messages in this thread | | | Subject | Re: [PATCH 2/4] block, bfq: avoid moving bfqq to it's parent bfqg | From | "yukuai (C)" <> | Date | Tue, 21 Dec 2021 19:08:44 +0800 |
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在 2021/12/21 18:16, Jan Kara 写道: > On Tue 21-12-21 11:21:33, Yu Kuai wrote: >> Moving bfqq to it's parent bfqg is pointless. >> >> Signed-off-by: Yu Kuai <yukuai3@huawei.com> > > Did you notice that this is happening often enough that the check is worth > it? Where do we do this? >
I noticed that this will happend when root group is offlined:
bfq_pd_offline bfq_put_async_queues __bfq_put_async_bfqq bfq_bfqq_move
I'm not sure if there are other situations. I think bfq_bfqq_move() is not happening often itself, thus the checking won't affect performance.
Thanks, Kuai > Honza > >> --- >> block/bfq-cgroup.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c >> index 24a5c5329bcd..0f62546a72d4 100644 >> --- a/block/bfq-cgroup.c >> +++ b/block/bfq-cgroup.c >> @@ -645,6 +645,11 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, >> struct bfq_group *bfqg) >> { >> struct bfq_entity *entity = &bfqq->entity; >> + struct bfq_group *old_parent = bfq_group(bfqq); >> + >> + /* No point to move bfqq to the same group */ >> + if (old_parent == bfqg) >> + return; >> >> /* >> * Get extra reference to prevent bfqq from being freed in >> @@ -666,7 +671,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, >> bfq_deactivate_bfqq(bfqd, bfqq, false, false); >> else if (entity->on_st_or_in_serv) >> bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); >> - bfqg_and_blkg_put(bfqq_group(bfqq)); >> + bfqg_and_blkg_put(old_parent); >> >> if (entity->parent && >> entity->parent->last_bfqq_created == bfqq) >> -- >> 2.31.1 >>
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