Commits
Shaohua Li committed f984df1f0f7
blk-mq: do limited block plug for multiple queue case plug is still helpful for workload with IO merge, but it can be harmful otherwise especially with multiple hardware queues, as there is (supposed) no lock contention in this case and plug can introduce latency. For multiple queues, we do limited plug, eg plug only if there is request merge. If a request doesn't have merge with following request, the requet will be dispatched immediately. V2: check blk_queue_nomerges() as suggested by Jeff. Cc: Jens Axboe <axboe@fb.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>