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I have a rtl8821ae-based 5GHz WiFi card on my desktop PC (It is pci-e TP-Link Archer T4E)

I would like to install and use Linux to this desktop. I try different popular distros (Ubuntu, Fedora, Manjaro etc) and for all of them there is the same problem: slow wi-fi speed. I googled and tried to build some drivers from GitHub, but the ones I found are for rtl8821aU (USB-version), while mine card is PCI-e.

I almost gave up, but tried Linux Mint Cinnamon and finally Wi-Fi worked as expected at full speed! Then I assumed Linux Mint uses some special driver. I decided that I need to figure out which one is used by Linux Mint to have a freedom to choose distro.

I found the answer here: How to find out which Wi-Fi driver is installed?

Below is my output of Ubuntu (which has terribly slow Wi-Fi):

user@ubnt:~$ sudo lshw -class network
[sudo] password for user: 
  *-network                 
       description: Wireless interface
       product: RTL8812AE 802.11ac PCIe Wireless Network Adapter
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 01
       serial: xx:xx:xx:xx:xx:xx
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rtl8821ae driverversion=5.8.0-48-generic firmware=N/A ip=xx.xx.xx.xx latency=0 link=yes multicast=yes wireless=IEEE 802.11
       resources: irq:158 ioport:e000(size=256) memory:df400000-df403fff

user@ubnt:~$ lsmod | grep rtl8821ae
rtl8821ae             233472  0
btcoexist             155648  1 rtl8821ae
rtl_pci                28672  1 rtl8821ae
rtlwifi                94208  3 rtl_pci,rtl8821ae,btcoexist
mac80211              905216  3 rtl_pci,rtl8821ae,rtlwifi

user@ubnt:~$ modinfo rtl8821ae
filename:       /lib/modules/5.8.0-49-generic/kernel/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/rtl8821ae.ko
firmware:       rtlwifi/rtl8821aefw_29.bin
firmware:       rtlwifi/rtl8821aefw.bin
description:    Realtek 8821ae 802.11ac PCI wireless
license:        GPL
author:         Realtek WlanFAE    <[email protected]>
srcversion:     64BDAFD5093CE917B32291C
alias:          pci:v000010ECd00008821sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008812sv*sd*bc*sc*i*
depends:        rtlwifi,rtl_pci,btcoexist,mac80211
retpoline:      Y
intree:         Y
name:           rtl8821ae
vermagic:       5.8.0-49-generic SMP mod_unload modversions 
sig_id:         PKCS#7
signer:         Build time autogenerated kernel key
sig_key:        1A:D5:E6:56:CF:B6:5E:AF:60:74:90:89:34:8C:97:0F:89:36:10:FB
sig_hashalgo:   sha512
signature:      2C:62:21:33:F2:14:BA:C9:6D:A9:71:6F:92:6D:DE:4C:F5:B7:57:C5:
        BE:A2:F1:61:99:31:DE:15:3B:E2:42:41:FA:15:1D:2D:24:6F:6F:C6:
        B8:4B:2F:92:21:F8:D5:B6:E2:6E:9B:42:86:F1:43:CE:FC:DF:87:F8:
        8D:DC:BB:65:A3:5E:7C:42:2C:46:CA:EB:48:59:44:A7:83:36:91:6A:
        C8:21:AC:F7:CD:71:7C:E4:59:FF:11:E4:4A:2B:C5:AF:FD:88:EE:F7:
        8E:B8:FA:A6:B8:A9:35:5F:76:A4:8A:D7:63:E0:37:74:BE:91:34:F1:
        E6:F8:DB:6F:D5:AF:3D:C6:29:26:51:95:8F:3C:4F:65:A5:05:0B:19:
        20:ED:1D:D2:F0:FF:F1:F1:06:C3:51:06:20:2F:40:11:E6:12:C4:96:
        1F:C1:C5:58:7D:09:10:C3:17:DE:31:51:2E:14:DE:92:20:40:62:D2:
        0A:D6:52:73:37:10:28:30:EA:47:28:53:51:2D:5C:C2:F7:10:E2:44:
        58:67:83:6B:F1:5D:01:A4:A6:B2:EC:B7:FD:CC:A4:A9:DD:71:13:91:
        52:E0:77:A6:E6:1A:4A:27:B0:0A:59:EF:EF:28:D4:E3:CE:A9:8F:DD:
        F5:A0:FF:91:02:E6:E4:2E:D9:08:90:F0:AB:E2:67:AA:B1:54:A2:7E:
        8A:77:97:FB:93:1C:85:CC:E5:18:CE:F9:AC:47:9E:8D:D3:2F:9C:11:
        16:38:E6:DC:BA:D6:8C:C7:EA:B9:38:EE:27:00:AE:66:FE:CB:79:E0:
        43:66:2D:5C:88:AE:BD:07:49:08:F2:4E:4D:BF:FE:48:3E:6D:14:3A:
        CC:DE:7D:02:8A:6E:E6:72:69:FB:65:30:36:35:DD:5B:FA:DD:1B:F4:
        B5:F2:56:05:A6:58:C0:31:0A:93:BB:05:F1:B4:5D:0A:32:4A:38:46:
        1B:9F:F9:27:8B:A0:56:CE:14:8B:84:C8:56:7D:24:FD:50:0F:6E:E8:
        E8:5F:9E:7C:C1:6B:50:AB:68:BE:23:3F:27:84:82:B1:64:6C:DF:C5:
        CC:6B:33:7C:B4:5E:1A:8D:61:E1:D9:58:EA:3F:19:DD:C9:92:ED:18:
        FC:A4:96:94:EF:F4:C1:9F:63:E8:E9:83:2B:CF:DC:28:38:F6:86:C4:
        20:7C:C6:8E:F7:64:CE:D9:B0:F1:19:D8:E2:1F:EB:77:3D:24:C3:93:
        23:FC:69:16:DA:27:64:6F:92:88:91:EA:25:FF:BB:F1:30:19:0F:74:
        68:C1:EB:C1:F0:A5:2C:F7:F4:03:30:72:50:28:EB:54:F0:84:F6:17:
        60:27:3F:54:89:E1:25:A8:07:12:AC:0B
parm:           swenc:Set to 1 for software crypto (default 0)
 (bool)
parm:           ips:Set to 0 to not use link power save (default 1)
 (bool)
parm:           swlps:Set to 1 to use SW control power save (default 0)
 (bool)
parm:           fwlps:Set to 1 to use FW control power save (default 1)
 (bool)
parm:           msi:Set to 1 to use MSI interrupts mode (default 1)
 (bool)
parm:           aspm:Set to 1 to enable ASPM (default 1)
 (int)
parm:           debug_level:Set debug level (0-5) (default 0) (int)
parm:           debug_mask:Set debug mask (default 0) (ullong)
parm:           disable_watchdog:Set to 1 to disable the watchdog (default 0)
 (bool)
parm:           int_clear:Set to 0 to disable interrupt clear before set (default 1)
 (bool)

Now the output of well behaving Linux Mint:

mint@mint:~/Desktop$ sudo lshw -class network
  *-network                 
       description: Wireless interface
       product: RTL8812AE 802.11ac PCIe Wireless Network Adapter
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 01
       serial: xx:xx:xx:xx:xx:xx
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rtl8821ae driverversion=5.4.0-58-generic firmware=N/A ip=xx.xx.xx.xx latency=0 link=yes multicast=yes wireless=IEEE 802.11
       resources: irq:159 ioport:e000(size=256) memory:df400000-df403fff

mint@mint:~/Desktop$ lsmod | grep rtl8821ae
rtl8821ae             233472  0
btcoexist             155648  1 rtl8821ae
rtl_pci                28672  1 rtl8821ae
rtlwifi                90112  3 rtl_pci,rtl8821ae,btcoexist
mac80211              843776  3 rtl_pci,rtl8821ae,rtlwifi

mint@mint:~$ modinfo rtl8821ae
filename:       /lib/modules/5.4.0-58-generic/kernel/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/rtl8821ae.ko
firmware:       rtlwifi/rtl8821aefw_29.bin
firmware:       rtlwifi/rtl8821aefw.bin
description:    Realtek 8821ae 802.11ac PCI wireless
license:        GPL
author:         Realtek WlanFAE    <[email protected]>
srcversion:     A8B43BD1DD5C4F8EC9C4F6A
alias:          pci:v000010ECd00008821sv*sd*bc*sc*i*
alias:          pci:v000010ECd00008812sv*sd*bc*sc*i*
depends:        rtlwifi,rtl_pci,btcoexist,mac80211
retpoline:      Y
intree:         Y
name:           rtl8821ae
vermagic:       5.4.0-58-generic SMP mod_unload 
sig_id:         PKCS#7
signer:         Build time autogenerated kernel key
sig_key:        4F:99:95:CB:A3:36:65:3E:1E:5A:30:73:58:12:C3:10:81:02:EA:FF
sig_hashalgo:   sha512
signature:      04:58:B3:93:74:BB:47:4C:44:EC:B9:B4:BF:41:D8:2F:78:10:5E:74:
        CD:E2:93:42:71:D7:48:C7:ED:DA:9C:80:00:BB:DF:99:2A:44:0C:CB:
        BF:79:2E:05:FD:61:CA:E7:3F:5A:C0:5D:1B:78:31:41:88:44:A4:6A:
        82:A8:51:64:AA:12:6F:1A:F2:09:E8:C1:5E:CF:BA:52:2F:8E:1D:DF:
        D9:93:8E:51:EF:4D:7E:8E:2E:D6:B1:DE:3E:05:0C:57:05:3E:3B:70:
        62:F6:01:87:A0:16:41:90:AF:CA:B9:7B:98:C8:DF:E0:2A:74:C1:97:
        DD:9B:23:93:C5:32:28:07:C0:72:52:C6:62:89:90:6C:A3:B2:80:E5:
        DE:E5:78:C5:FF:75:C9:3F:42:53:35:E4:9A:D7:A3:82:0B:BE:B8:90:
        0D:AD:0C:6D:48:A6:40:32:2E:2E:11:9D:55:C5:2A:4D:4F:40:EF:36:
        B2:F7:E5:C0:2E:56:C5:8C:13:27:86:C2:F1:0E:27:0F:9A:64:EE:CA:
        29:B7:A8:56:4D:7B:71:A2:B4:01:FA:1E:DC:7C:3A:B5:32:07:29:EF:
        86:41:94:61:64:17:6B:DD:B8:6D:9B:7C:2D:56:9D:5E:69:7B:A1:A8:
        C5:62:A5:F7:43:2D:49:D7:6A:43:3C:1B:DC:28:74:BF:0E:7E:BD:47:
        41:DF:0C:9E:E0:D3:5E:A9:9C:3C:6A:67:05:57:A7:9A:00:54:07:46:
        AE:53:5B:8F:8F:1C:76:AA:7E:41:FA:23:70:00:4F:BA:59:92:91:A9:
        F7:7B:16:B2:0B:DB:1A:43:A4:00:EF:3A:A7:5D:D0:E9:D0:80:CF:C6:
        77:0F:E7:75:99:C7:80:66:7D:94:E4:88:F1:22:26:69:D5:1E:F1:79:
        C4:14:E8:B9:20:66:9C:72:DD:02:85:EA:A3:51:02:03:97:C5:65:60:
        3E:E7:94:AD:A5:DA:ED:EC:34:BC:2E:41:48:BF:1C:B8:C0:3B:95:39:
        A8:A8:AC:57:3C:95:91:BA:E5:38:A3:82:34:BD:85:CA:71:3D:45:4A:
        4D:D7:13:54:57:9B:7B:BD:67:B2:DE:77:05:60:5D:B9:71:0E:B7:D4:
        45:88:2D:F8:0C:FD:20:EF:A8:AE:51:B0:25:5F:E6:85:36:24:C0:10:
        A9:49:EA:05:BD:27:C6:01:1D:83:48:03:F5:B1:08:DA:86:0F:F8:68:
        BB:7E:6D:01:76:36:D1:EE:B2:F2:72:D2:9F:E6:12:E4:77:DF:5A:1C:
        E4:9F:3E:14:62:DF:8F:D5:2A:A6:04:88:39:07:6E:BB:78:5A:74:2B:
        F5:D3:70:56:2F:D1:09:2C:B7:48:88:FF
parm:           swenc:Set to 1 for software crypto (default 0)
 (bool)
parm:           ips:Set to 0 to not use link power save (default 1)
 (bool)
parm:           swlps:Set to 1 to use SW control power save (default 0)
 (bool)
parm:           fwlps:Set to 1 to use FW control power save (default 1)
 (bool)
parm:           msi:Set to 1 to use MSI interrupts mode (default 1)
 (bool)
parm:           aspm:Set to 1 to enable ASPM (default 1)
 (int)
parm:           debug_level:Set debug level (0-5) (default 0) (int)
parm:           debug_mask:Set debug mask (default 0) (ullong)
parm:           disable_watchdog:Set to 1 to disable the watchdog (default 0)
 (bool)
parm:           int_clear:Set to 0 to disable interrupt clear before set (default 1)
 (bool)

Looks like driver name matches. And driver version gives me a clue that it is a driver from the kernel. While driver module size (according to lsmod) is equal and the driver version is greater for Ubuntu, how comes it is so slow on any distro but Mint? What else can I check to figure out the difference and how can I enable fast Wi-Fi on any other distro? With Linux Mint now I know for sure that it is possible.

UPD: added modinfo output. The srcversion differs (as expected). The Linux Mint kernel/driver version is older. If it is a regression in newer Realtek driver/kernel, what is the best place to submit a bug report?

UPD2: If I update linux Kernel from 5.4 to 5.8, wifi becomes slow. Looks like I need to submit a kernel bug. But before it I would like to check if the latest stable kernel (5.11) have the problem.

2
  • What is your WiFi MTU? ip link show.
    – waltinator
    Apr 13, 2021 at 19:52
  • @waltinator mtu 1500 with slow WiFi
    – Kirill
    Apr 13, 2021 at 20:03

1 Answer 1

Reset to default
0

Check your WiFi MTU, using

ip link

also notice your WiFi interface's name.

The MTU (Maximum Transmission Unit) is the size of the largest packet that can be sent in a single network transmission. If a packet exceeds the MTU of a link, the data must be split into multiple packets (fragmented). These multiple packets must be sent over the link, received, acknowledged, and reassembled at the far end. If your link is misconfigured, and you have to fragment every packet you send, your actual data transfer rate drops.

Ethernet (wired) networks use an MTU of 1500 bytes.

Due to additional per packet overhead for WiFi (8 bytes PPPoE header), WiFi uses an MTU of 1492.

Your MTU should be set by your DHCP server, check your router's config.

You can set your own MTU (setting does not persist over restarts) with

ip link set dev name mtu 1492

where "name" is the interface name from above.

Here's an example:

walt@squid:~(0)$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp63s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:24:21:7f:e5:1c brd ff:ff:ff:ff:ff:ff
3: wlxf46d04b1790f: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
    link/ether f4:6d:04:b1:79:0f brd ff:ff:ff:ff:ff:ff
walt@squid:~(0)$   sudo ip link set dev wlxf46d04b1790f mtu 1492
[sudo] password for walt: 
walt@squid:~(0)$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp63s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:24:21:7f:e5:1c brd ff:ff:ff:ff:ff:ff
3: wlxf46d04b1790f: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1492 qdisc mq state UP mode DORMANT group default qlen 1000
    link/ether f4:6d:04:b1:79:0f brd ff:ff:ff:ff:ff:ff

My WiFi "interface name" is "wlxf46d04b1790f".

1
  • The MTU is 1500 for both fast (Mint) and slow (other distros) wifi. I tried to set 1492, no effect
    – Kirill
    Apr 13, 2021 at 20:30

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