Messages in this thread | | | Date | Wed, 30 Nov 2022 11:09:20 -1000 | From | Tejun Heo <> | Subject | Re: [PATCH v2 02/10] blk-throttle: Fix that bps of child could exceed bps limited in parent |
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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>
-- tejun
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