block, bfq: re-evaluate convenience of I/O plugging on rq arrivals

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Upon an I/O-dispatch attempt, BFQ may detect that it was better to
plug I/O dispatch, and to wait for a new request to arrive for the
currently in-service queue. But the arrival of a new request for an
empty bfq_queue, and thus the switch from idle to busy of the
bfq_queue, may cause the scenario to change, and make plugging no
longer needed for service guarantees, or more convenient for
throughput. In this case, keeping I/O-dispatch plugged would certainly
lower throughput.

To address this issue, this commit makes such a check, and stops
plugging I/O if it is better to stop plugging I/O.

Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Paolo Valente 2021-01-25 20:02:44 +01:00 • committed by Jens Axboe

parent eb2fd80f9d

commit 7f1995c27b

1 changed files with 19 additions and 5 deletions

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block/bfq-iosched.c

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