4045 zfs write throttle & i/o scheduler performance work
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>

*** 430,440 ****
                          }
  
                          zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
                              mc->mc_vd, mc->mc_offset,
                              zio->io_data, zio->io_size,
!                             ZIO_TYPE_WRITE, zio->io_priority,
                              ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
                              ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
                  }
          }
  }
--- 430,440 ----
                          }
  
                          zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
                              mc->mc_vd, mc->mc_offset,
                              zio->io_data, zio->io_size,
!                             ZIO_TYPE_WRITE, ZIO_PRIORITY_ASYNC_WRITE,
                              ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
                              ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
                  }
          }
  }