BENCH_ZIO_SIZE
speed = run_cnt * BENCH_ZIO_SIZE * NANOSEC;
bench_zio->io_size = BENCH_ZIO_SIZE; /* only data columns */
bench_zio->io_abd = abd_alloc_linear(BENCH_ZIO_SIZE, B_TRUE);
memset(abd_to_buf(bench_zio->io_abd), 0xAA, BENCH_ZIO_SIZE);