From: Ming Lei ming.lei@redhat.com
[ Upstream commit 9f5ede3c01f9951b0ae7d68b28762ad51d9bacc8 ]
Commit 111be8839817 ("block-throttle: avoid double charge") marks bio as BIO_THROTTLED unconditionally if __blk_throtl_bio() is called on this bio, then this bio won't be called into __blk_throtl_bio() any more. This way is to avoid double charge in case of bio splitting. It is reasonable for read/write throughput limit, but not reasonable for IOPS limit because block layer provides io accounting against split bio.
Chunguang Xu has already observed this issue and fixed it in commit 4f1e9630afe6 ("blk-throtl: optimize IOPS throttle for large IO scenarios"). However, that patch only covers bio splitting in __blk_queue_split(), and we have other kind of bio splitting, such as bio_split() & submit_bio_noacct() and other ways.
This patch tries to fix the issue in one generic way by always charging the bio for iops limit in blk_throtl_bio(). This way is reasonable: re-submission & fast-cloned bio is charged if it is submitted to same disk/queue, and BIO_THROTTLED will be cleared if bio->bi_bdev is changed.
This new approach can get much more smooth/stable iops limit compared with commit 4f1e9630afe6 ("blk-throtl: optimize IOPS throttle for large IO scenarios") since that commit can't throttle current split bios actually.
Also this way won't cause new double bio iops charge in blk_throtl_dispatch_work_fn() in which blk_throtl_bio() won't be called any more.
Reported-by: Ning Li lining2020x@163.com Acked-by: Tejun Heo tj@kernel.org Cc: Chunguang Xu brookxu@tencent.com Signed-off-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20220216044514.2903784-7-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-merge.c | 2 -- block/blk-throttle.c | 10 +++++++--- block/blk-throttle.h | 2 -- 3 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c index a5b73bad9462..09bf679dc132 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -367,8 +367,6 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio, trace_block_split(split, (*bio)->bi_iter.bi_sector); submit_bio_noacct(*bio); *bio = split; - - blk_throtl_charge_bio_split(*bio); } }
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 39bb6e68a9a2..96573fa4edf2 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -807,7 +807,8 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; unsigned int bio_size = throtl_bio_data_size(bio);
- if (bps_limit == U64_MAX) { + /* no need to throttle if this bio's bytes have been accounted */ + if (bps_limit == U64_MAX || bio_flagged(bio, BIO_THROTTLED)) { if (wait) *wait = 0; return true; @@ -919,9 +920,12 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) unsigned int bio_size = throtl_bio_data_size(bio);
/* Charge the bio to the group */ - tg->bytes_disp[rw] += bio_size; + if (!bio_flagged(bio, BIO_THROTTLED)) { + tg->bytes_disp[rw] += bio_size; + tg->last_bytes_disp[rw] += bio_size; + } + tg->io_disp[rw]++; - tg->last_bytes_disp[rw] += bio_size; tg->last_io_disp[rw]++;
/* diff --git a/block/blk-throttle.h b/block/blk-throttle.h index 175f03abd9e4..cb43f4417d6e 100644 --- a/block/blk-throttle.h +++ b/block/blk-throttle.h @@ -170,8 +170,6 @@ static inline bool blk_throtl_bio(struct bio *bio) { struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
- if (bio_flagged(bio, BIO_THROTTLED)) - return false; if (!tg->has_rules[bio_data_dir(bio)]) return false;