| Message ID | 20221129030147.27400-3-shikemeng@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | A few bugfix and cleanup patches for blk-throttle | expand |
On Tue, Nov 29, 2022 at 11:01:39AM +0800, Kemeng Shi wrote: > 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 only set BIO_BPS_THROTTLED when the bio traversed the entire > tree. > > There patch has 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@huawei.com> Acked-by: Tejun Heo <tj@kernel.org>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 59acfac87764..d516a37e82fb 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -1067,7 +1067,6 @@ static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) sq->nr_queued[rw]--; throtl_charge_bio(tg, bio); - bio_set_flag(bio, BIO_BPS_THROTTLED); /* * If our parent is another tg, we just need to transfer @bio to @@ -1080,6 +1079,7 @@ static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg); start_parent_slice_with_credit(tg, parent_tg, rw); } else { + bio_set_flag(bio, BIO_BPS_THROTTLED); throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], &parent_sq->queued[rw]); BUG_ON(tg->td->nr_queued[rw] <= 0);
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 only set BIO_BPS_THROTTLED when the bio traversed the entire tree. There patch has 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@huawei.com> --- block/blk-throttle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)