Consider situation as following (on the default hierarchy):
HDD
|
root (bps limit: 4k)
|
child (bps limit :8k)
|
fio bs=8k
Rate of fio is supposed to be 4k, but result is 8k. Reason is as
following:
Size of single IO from fio is larger than bytes allowed in one
throtl_slice in child, so IOs are always queued in child group first.
When queued IOs in child are dispatched to parent group, BIO_BPS_THROTTLED
is set and these IOs will not be limited by tg_within_bps_limit anymore.
Fix this by:
1. Limit IO with BIO_BPS_THROTTLED flag in tg_within_bps_limit.
2. Ignore BIO_BPS_THROTTLED flag when accouting in throtl_charge_bio.
There changes have no influence on situation which is not on the default
hierarchy as each group is a single root group without parent.
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxx>
---
block/blk-throttle.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 96aa53e30e28..b33bcf53b36e 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -856,8 +856,7 @@ static bool tg_within_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);
- /* no need to throttle if this bio's bytes have been accounted */
- if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
+ if (bps_limit == U64_MAX) {
if (wait)
*wait = 0;
return true;
@@ -964,10 +963,8 @@ 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 */
- if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
- tg->bytes_disp[rw] += bio_size;
- tg->last_bytes_disp[rw] += bio_size;
- }
+ tg->bytes_disp[rw] += bio_size;
+ tg->last_bytes_disp[rw] += bio_size;
tg->io_disp[rw]++;
tg->last_io_disp[rw]++;
--
2.30.0
