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authorKemeng Shi <shikemeng@huawei.com>2022-12-05 19:57:02 +0800
committerJens Axboe <axboe@kernel.dk>2022-12-05 13:44:27 -0700
commit84aca0a7e039c8735abc0f89f3f48e9006c0dfc7 (patch)
tree2c558db44b8ff430c08d41a8f92f3789e7eb99d6 /block/blk-throttle.c
parentf56019aef353576f43f945fdd065858145090582 (diff)
downloadlwn-84aca0a7e039c8735abc0f89f3f48e9006c0dfc7.tar.gz
lwn-84aca0a7e039c8735abc0f89f3f48e9006c0dfc7.zip
blk-throttle: Fix that bps of child could exceed bps limited in parent
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. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Kemeng Shi <shikemeng@huawei.com> Link: https://lore.kernel.org/r/20221205115709.251489-3-shikemeng@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8e2349b17936..2444ebf5f11d 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);