• Keith Busch's avatar
    blk-mq: dynamic h/w context count · 868f2f0b
    Keith Busch authored
    The hardware's provided queue count may change at runtime with resource
    provisioning. This patch allows a block driver to alter the number of
    h/w queues available when its resource count changes.
    The main part is a new blk-mq API to request a new number of h/w queues
    for a given live tag set. The new API freezes all queues using that set,
    then adjusts the allocated count prior to remapping these to CPUs.
    The bulk of the rest just shifts where h/w contexts and all their
    artifacts are allocated and freed.
    The number of max h/w contexts is capped to the number of possible cpus
    since there is no use for more than that. As such, all pre-allocated
    memory for pointers need to account for the max possible rather than
    the initial number of queues.
    A side effect of this is that the blk-mq will proceed successfully as
    long as it can allocate at least one h/w context. Previously it would
    fail request queue initialization if less than the requested number
    was allocated.
    Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Tested-by: default avatarJon Derrick <jonathan.derrick@intel.com>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
blk-mq.h 3.27 KB