$ lsusb
Bus 001 Device 005: ID 0cf3:9271 Atheros Communications, Inc. AR9271 802.11n
$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether bc:ae:c5:b8:0c:54 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 54:e6:fc:02:48:26 brd ff:ff:ff:ff:ff:ff
inet 192.168.5.102/24 brd 192.168.5.255 scope global dynamic wlan0
valid_lft 4596sec preferred_lft 4596sec
inet6 fe80::8f64:ff57:d9db:e4e1/64 scope link
valid_lft forever preferred_lft forever
安装完 Deiban 9之后，无线网卡的名很长，虽然发现了无线网络，但登录下上去。查了一下，在grub里做了设置http://www.itzgeek.com/how-tos/linux/debian/change-default-network-name-ens33-to-old-eth0-on-debian-9.html，恢复了旧名。就能正常上网了。
现在网卡能工作，但感觉网特别慢。猜想是驱动没安装对。请教如何诊断。