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@xxxxxxxxxx>
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
