• Ming Lei's avatar
    blk-mq: support per-distpatch_queue flush machinery · f70ced09
    Ming Lei authored
    This patch supports to run one single flush machinery for
    each blk-mq dispatch queue, so that:
    
    - current init_request and exit_request callbacks can
    cover flush request too, then the buggy copying way of
    initializing flush request's pdu can be fixed
    
    - flushing performance gets improved in case of multi hw-queue
    
    In fio sync write test over virtio-blk(4 hw queues, ioengine=sync,
    iodepth=64, numjobs=4, bs=4K), it is observed that througput gets
    increased a lot over my test environment:
    	- throughput: +70% in case of virtio-blk over null_blk
    	- throughput: +30% in case of virtio-blk over SSD image
    
    The multi virtqueue feature isn't merged to QEMU yet, and patches for
    the feature can be found in below tree:
    
    	git://kernel.ubuntu.com/ming/qemu.git
    
      	v2.1.0-mq.4
    
    And simply passing 'num_queues=4 vectors=5' should be enough to
    enable multi queue(quad queue) feature for QEMU virtio-blk.
    Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: Ming Lei <min...
    f70ced09
blk-flush.c 14.8 KB