• Tejun Heo's avatar
    blkcg: use radix tree to index blkgs from blkcg · a637120e
    Tejun Heo authored
    
    
    blkg lookup is currently performed by traversing linked list anchored
    at blkcg->blkg_list.  This is very unscalable and with blk-throttle
    enabled and enough request queues on the system, this can get very
    ugly quickly (blk-throttle performs look up on every bio submission).
    
    This patch makes blkcg use radix tree to index blkgs combined with
    simple last-looked-up hint.  This is mostly identical to how icqs are
    indexed from ioc.
    
    Note that because __blkg_lookup() may be invoked without holding queue
    lock, hint is only updated from __blkg_lookup_create().  Due to cfq's
    cfqq caching, this makes hint updates overly lazy.  This will be
    improved with scheduled blkcg aware request allocation.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Vivek Goyal <vgoyal@redhat.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    a637120e