• Jens Axboe's avatar
    blk-mq: improve support for shared tags maps · 0d2602ca
    Jens Axboe authored
    This adds support for active queue tracking, meaning that the
    blk-mq tagging maintains a count of active users of a tag set.
    This allows us to maintain a notion of fairness between users,
    so that we can distribute the tag depth evenly without starving
    some users while allowing others to try unfair deep queues.
    If sharing of a tag set is detected, each hardware queue will
    track the depth of its own queue. And if this exceeds the total
    depth divided by the number of active queues, the user is actively
    throttled down.
    The active queue count is done lazily to avoid bouncing that data
    between submitter and completer. Each hardware queue gets marked
    active when it allocates its first tag, and gets marked inactive
    when 1) the last tag is cleared, and 2) the queue timeout grace
    period has passed.
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
blk-mq-sysfs.c 9.4 KB