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authorPaolo Valente <paolo.valente@linaro.org>2018-06-25 22:55:35 +0300
committerJens Axboe <axboe@kernel.dk>2018-07-09 18:07:52 +0300
commit4420b095cc474759f6fbdb6351648c7ff9833a54 (patch)
tree6cda6a5d78a993bf317ac1ba734f1d0f18420d9e /block/bfq-wf2q.c
parent0471559c2fbd2c19d183fc0f51ce88aefa0a13c8 (diff)
downloadlinux-4420b095cc474759f6fbdb6351648c7ff9833a54.tar.xz
block, bfq: do not expire a queue that will deserve dispatch plugging
For some bfq_queues, BFQ plugs I/O dispatching when the queue becomes idle, and keeps the plug until a new request of the queue arrives, or a timeout fires. BFQ does so either to boost throughput or to preserve service guarantees for the queue. More precisely, for such a queue, plugging starts when the queue happens to have either no request enqueued, or no request in flight, that is, no request already dispatched but not yet completed. On the opposite end, BFQ may happen to expire a queue with no request enqueued, without doing any plugging, if the queue still has some request in flight. Unfortunately, such a premature expiration causes the queue to lose its chance to enjoy dispatch plugging a moment later, i.e., when its in-flight requests finally get completed. This breaks service guarantees for the queue. This commit prevents BFQ from expiring an empty queue if the latter still has in-flight requests. Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-wf2q.c')
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