[PATCH RFC 0/7] blk-mq: improve tag fair sharing

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

This is not a formal version and not fully tested, I send this RFC
because I want to make sure if people think doing this is meaningful,
before I spend too much time on this.

This patchset tries to refactor how tag is shared:
 - patch 2 delay tag sharing from issue io to when get driver tag faild;
 - patch 3 support to access which queues/hctxs is sharing tags through
 blk_mq_tags;
 - patch 4 move the caculation that how many tags is available from
 hctx_may_queue() to when queue/hctx start or stop to sharing tags.
 - patch 5 record new information that how many times fail to get driver
 tag recently; And patch 7 use this to adjust available tags for each
 shared queue.

Yu Kuai (7):
  blk-mq: factor out a structure from blk_mq_tags to control tag sharing
  blk-mq: delay tag fair sharing until fail to get driver tag
  blk-mq: support to track active queues from blk_mq_tags
  blk-mq: precalculate available tags for hctx_may_queue()
  blk-mq: record the number of times fail to get driver tag while
    sharing tags
  blk-mq: move active request counter to struct tag_sharing
  blk-mq: allow shared queue to get more driver tags

 block/blk-core.c       |   2 -
 block/blk-mq-debugfs.c |   6 +-
 block/blk-mq-tag.c     | 154 ++++++++++++++++++++++++++++++++++++++---
 block/blk-mq.c         |  10 ++-
 block/blk-mq.h         |  39 ++++++-----
 include/linux/blk-mq.h |  24 ++++---
 include/linux/blkdev.h |  13 +++-
 7 files changed, 201 insertions(+), 47 deletions(-)

-- 
2.39.2