On Tue 21-12-21 19:08:44, yukuai (C) wrote:

在 2021/12/21 18:16, Jan Kara 写道:

quoted

On Tue 21-12-21 11:21:33, Yu Kuai wrote:

quoted

Moving bfqq to it's parent bfqg is pointless.

Signed-off-by: Yu Kuai <redacted>

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.

Yeah, OK, I was just wondering. I guess there's no harm in doing this
check. Maybe add a comment that this can sometimes happen when dealing with
the root cgroup. And then feel free to add:

Reviewed-by: Jan Kara <redacted>

								Honza

-- 
Jan Kara [off-list ref]
SUSE Labs, CR