1. 09 Oct, 2018 39 commits
  2. 08 Oct, 2018 1 commit
    • Ming Lei's avatar
      blk-mq: complete req in softirq context in case of single queue · 36e76539
      Ming Lei authored
      Lot of controllers may have only one irq vector for completing IO
      request. And usually affinity of the only irq vector is all possible
      CPUs, however, on most of ARCH, there may be only one specific CPU
      for handling this interrupt.
      
      So if all IOs are completed in hardirq context, it is inevitable to
      degrade IO performance because of increased irq latency.
      
      This patch tries to address this issue by allowing to complete request
      in softirq context, like the legacy IO path.
      
      IOPS is observed as ~13%+ in the following randread test on raid0 over
      virtio-scsi.
      
      mdadm --create --verbose /dev/md0 --level=0 --chunk=1024 --raid-devices=8 /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi
      
      fio --time_based --name=benchmark --runtime=30 --filename=/dev/md0 --nrfiles=1 --ioengine=libaio --iodepth=32 --direct=1 --invalidate=1 --verify=0 --verify_fatal=0 --numjobs=32 --rw=randread --blocksize=4k
      
      Cc: Dongli Zhang <dongli.zhang@oracle.com>
      Cc: Zach Marano <zmarano@google.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Bart Van Assche <bvanassche@acm.org>
      Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
      Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      36e76539