[PATCH 0/3] fix the performance fluctuation due to shared tagset

[Yu Kuai]

The problem is due to the max number of avaliable tags is
max(total tags / active_queues, 4).

We fix it by ensuring the following:
a. don't restrict if the utilization rate of total tags is less than
100%
b. if the utilization rate of total tags is 100%, and someone failed
to get driver tag, start to restrict as before.
b. if the utilization rate of total tags goes below 100%, it can
stop to restrict quickly.

Yu Kuai (3):
  blk-mq: allow hardware queue to get more tag while sharing a tag set
  blk-mq: clear 'active_queues' immediately when 'nr_active' is
    decreased to 0
  blk-mq: decrease pending_queues when it expires

 block/blk-mq-debugfs.c |  2 ++
 block/blk-mq-tag.c     | 61 +++++++++++++++++++++++++++++++++++++++++-
 block/blk-mq-tag.h     | 23 ++++++++++++++++
 block/blk-mq.c         |  9 +++++--
 block/blk-mq.h         | 11 +++++---
 include/linux/blk-mq.h | 10 ++++++-
 include/linux/blkdev.h |  1 +
 7 files changed, 110 insertions(+), 7 deletions(-)

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2.25.4