Hello, Shaohua. On Fri, Oct 13, 2017 at 11:10:29AM -0700, Shaohua Li wrote: > If a bio is throttled and splitted after throttling, the bio could be > resubmited and enters the throttling again. This will cause part of the > bio is charged multiple times. If the cgroup has an IO limit, the double > charge will significantly harm the performance. The bio split becomes > quite common after arbitrary bio size change. Missed the patch previously. Sorry about that. > Some sort of this patch probably should go into stable since v4.2 Seriously. > @@ -2130,9 +2130,15 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg, > > WARN_ON_ONCE(!rcu_read_lock_held()); > > - /* see throtl_charge_bio() */ > - if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw]) > + /* > + * see throtl_charge_bio() for BIO_THROTTLED. If a bio is throttled > + * against a disk but remapped to other disk, we should throttle it > + * again > + */ > + if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw] || > + (bio->bi_throttled_disk && bio->bi_throttled_disk == bio->bi_disk)) > goto out; > + bio->bi_throttled_disk = NULL; So, one question I have is whether we need both BIO_THROTTLED and bi_throttled_disk. Can't we replace BIO_THROTTLED w/ bi_throttled_disk? Thanks. -- tejun
