POSIX_FADV_RANDOM
CTASSERT(POSIX_FADV_RANDOM == UVM_ADV_RANDOM);
case POSIX_FADV_RANDOM:
CE(posix_fadvise(fd, 0, 0, POSIX_FADV_RANDOM), 0);
CE(rump_sys_posix_fadvise(rfd, 0, 0, POSIX_FADV_RANDOM), 0);
INT64_MAX-getpagesize(), getpagesize(), POSIX_FADV_RANDOM), 0);