• Chris Mason's avatar
    Btrfs: Add async worker threads for pre and post IO checksumming · 8b712842
    Chris Mason authored
    Btrfs has been using workqueues to spread the checksumming load across
    other CPUs in the system.  But, workqueues only schedule work on the
    same CPU that queued the work, giving them a limited benefit for systems with
    higher CPU counts.
    
    This code adds a generic facility to schedule work with pools of kthreads,
    and changes the bio submission code to queue bios up.  The queueing is
    important to make sure large numbers of procs on the system don't
    turn streaming workloads into random workloads by sending IO down
    concurrently.
    
    The end result of all of this is much higher performance (and CPU usage) when
    doing checksumming on large machines.  Two worker pools are created,
    one for writes and one for endio processing.  The two could deadlock if
    we tried to service both from a single pool.
    Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
    8b712842
volumes.c 61.6 KB