tree 165fcba950a2f17a88639cf3251e660c3844f889
parent 0e7d3a8d4ec3f662faa7ef7f2957459b33f2481d
author Ming Lei <ming.lei@redhat.com> 1507972945 +0800
committer Jens Axboe <axboe@kernel.dk> 1509546002 -0600

blk-mq-sched: dispatch from scheduler IFF progress is made in ->dispatch

When the hw queue is busy, we shouldn't take requests from the scheduler
queue any more, otherwise it is difficult to do IO merge.

This patch fixes the awful IO performance on some SCSI devices(lpfc,
qla2xxx, ...) when mq-deadline/kyber is used by not taking requests if
hw queue is busy.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>