[PATCH v2 0/3] blk-mq: Optimise blk_mq_queue_tag_busy_iter() for shared tags

[John Garry]

In [0] Kashyap reports high CPU usage for blk_mq_queue_tag_busy_iter()
and callees for shared tags.

Indeed blk_mq_queue_tag_busy_iter() would be less optimum for moving to
shared tags, but it was not optimum previously.

This series optimises by having only a single iter (per regular and resv
tags) for the shared tags, instead of an iter per HW queue.

[0] https://lore.kernel.org/linux-block/e4e92abbe9d52bcba6b8cc6c91c442cc@xxxxxxxxxxxxxx/

Differences to v1:
- Add tested-by and reviewed-by tags
- Reformat 3/3 a bit to keep <= 80 char lines
	- I kept the RB tags, so please check and let me know if not ok
	  with the changes

John Garry (3):
  blk-mq: Drop busy_iter_fn blk_mq_hw_ctx argument
  blk-mq: Delete busy_iter_fn
  blk-mq: Optimise blk_mq_queue_tag_busy_iter() for shared tags

 block/blk-mq-tag.c     | 65 ++++++++++++++++++++++++++++--------------
 block/blk-mq-tag.h     |  2 +-
 block/blk-mq.c         | 17 ++++++-----
 include/linux/blk-mq.h |  2 --
 4 files changed, 53 insertions(+), 33 deletions(-)

-- 
2.26.2