tree fa40cb8073832b2321b3f28a3fd782c125364dfb
parent 8d354f133e86dd03ea7885a91df398c55ff699ff
author Jens Axboe <axboe@fb.com> 1472134050 -0600
committer Jens Axboe <axboe@fb.com> 1472480001 -0600

blk-mq: prefetch request in blk_mq_tag_to_rq()

When drivers or the core calls this function, they usually
dereference the request shortly there after. Prefetch the first
cache line.

Profiling IO workloads shows that this is the most common cache
miss on the block side of things.

Signed-off-by: Jens Axboe <axboe@fb.com>