dtrace -qn '
  enum zio_priority {
	ZIO_PRIORITY_SYNC_READ,
	ZIO_PRIORITY_SYNC_WRITE,	/* ZIL */
	ZIO_PRIORITY_ASYNC_READ,	/* prefetch */
	ZIO_PRIORITY_ASYNC_WRITE,	/* spa_sync() */
	ZIO_PRIORITY_SCRUB,		/* asynchronous scrub/resilver reads */
	ZIO_PRIORITY_NUM_QUEUEABLE,
	ZIO_PRIORITY_NOW		/* non-queued i/os (e.g. free) */
  } ;

  BEGIN {
    start = timestamp ;
    pri[ZIO_PRIORITY_SYNC_READ] = "Sync-Read" ;
    pri[ZIO_PRIORITY_SYNC_WRITE] = "Sync-Write" ;
    pri[ZIO_PRIORITY_ASYNC_READ] = "Async-Read" ;
    pri[ZIO_PRIORITY_ASYNC_WRITE] = "Async-Write" ;
    pri[ZIO_PRIORITY_SCRUB] = "Scrub" ;
    pri[ZIO_PRIORITY_NUM_QUEUEABLE] = "Queueable" ;
    pri[ZIO_PRIORITY_NOW] = "Non-queued" ;
    }
  ::zio_read:return, ::zio_write:return {
    @ops[pri[args[1]->io_priority]] = count() ;
    @[pri[args[1]->io_priority]] = quantize(args[1]->io_size) ;
  }
  END {
    /* normalize to operations per second */
    normalize(@ops, (timestamp - start) / 1000000000) ;
    printa("\tPRI: %s Ops/s: %@d%@d\n", @ops, @) ; }'