RTL8922AE: Severe latency spikes (>200ms) during wifi scan triggers

RTL8922AE: Severe latency spikes (>200ms) during wifi scan triggers

[Sivanantham Chinnaiyan]

Severe latency spikes (200ms+) occur whenever a Wi-Fi scan is
triggered (e.g., clicking Wi-Fi menu in GUI). This happens
consistently on both 2.4 GHz and 5 GHz networks, though it is much
more evident in 2.4GHz channel. I know that latency spikes during
scans are normal. But I am not sure if 150+ms is considered normal.

Hardware:
Chipset: Realtek rtw89_8922ae
Device: Lenovo Ideapad pro 5
Firmware version: [from dmesg | grep firmware] 0.35.80.3 (8ef4f0cf)
Kernel: fedora 6.19.13-200.fc43.x86_64

Software Stack:
Network Manager: NetworkManager (iwd backend)
Distribution: Fedora
Configuration: default

Steps to Reproduce:
1. Connect to a Wi-Fi network (2.4 GHz or 5 GHz)
2. Start continuous ping:
3. ```ping 8.8.8.8```
4.Open Wi-Fi menu in GUI (triggers scan)

Behavior:
Latency spikes to 200ms+ periodically
Happens every time a scan is triggered

Additional Observations:
Issue reproducible 100% of the time

Logs:
1. sudo dmesg | grep rtw

[    7.466016] rtw89_8922ae 0000:63:00.0: loaded firmware
rtw89/rtw8922a_fw-4.bin
[    7.466182] rtw89_8922ae 0000:63:00.0: enabling device (0000 -> 0003)
[    7.473628] rtw89_8922ae 0000:63:00.0: Firmware version 0.35.80.3
(8ef4f0cf), cmd version 1, type 1
[    7.473635] rtw89_8922ae 0000:63:00.0: Firmware version 0.35.80.3
(8ef4f0cf), cmd version 1, type 3
[    7.491846] rtw89_8922ae 0000:63:00.0: chip rfe_type is 1
[    7.494234] rtw89_8922ae 0000:63:00.0: Firmware version 0.1.0.0
(7b393818), cmd version 0, type 64
[    7.494239] rtw89_8922ae 0000:63:00.0: Firmware element BB version:
00 49 00 00
[    7.494244] rtw89_8922ae 0000:63:00.0: Firmware element radio A
version: 00 33 00 00
[    7.494252] rtw89_8922ae 0000:63:00.0: Firmware element NCTL
version: 00 0f 00 00
[    7.494296] rtw89_8922ae 0000:63:00.0: Firmware element TXPWR
version: 00 46 00 00
[    7.494297] rtw89_8922ae 0000:63:00.0: Firmware element TXPWR
version: 00 46 00 00
[    7.494297] rtw89_8922ae 0000:63:00.0: Firmware element TXPWR
version: 00 46 00 00
[    7.494307] rtw89_8922ae 0000:63:00.0: Firmware element PWR_TRK
version: 00 33 00 00
[    7.494313] rtw89_8922ae 0000:63:00.0: Firmware element REGD
version: 00 49 00 08
[    7.707799] rtw89_8922ae 0000:63:00.0: rfkill hardware state
changed to enable
[    7.717083] rtw89_8922ae 0000:63:00.0 wlp99s0: renamed from wlan0

2. ping -i 0.2 8.8.8.8 while connected to 2.4GHz( scan simulated using
`watch --interval=3 nmcli dev wifi rescan`)
)

64 bytes from 8.8.8.8: icmp_seq=24 ttl=118 time=34.9 ms
64 bytes from 8.8.8.8: icmp_seq=25 ttl=118 time=44.2 ms
64 bytes from 8.8.8.8: icmp_seq=26 ttl=118 time=6.61 ms
64 bytes from 8.8.8.8: icmp_seq=27 ttl=118 time=4.51 ms
64 bytes from 8.8.8.8: icmp_seq=28 ttl=118 time=92.3 ms
64 bytes from 8.8.8.8: icmp_seq=29 ttl=118 time=82.8 ms
64 bytes from 8.8.8.8: icmp_seq=30 ttl=118 time=20.4 ms
64 bytes from 8.8.8.8: icmp_seq=31 ttl=118 time=306 ms
64 bytes from 8.8.8.8: icmp_seq=32 ttl=118 time=102 ms
64 bytes from 8.8.8.8: icmp_seq=33 ttl=118 time=59.3 ms
64 bytes from 8.8.8.8: icmp_seq=34 ttl=118 time=183 ms
64 bytes from 8.8.8.8: icmp_seq=35 ttl=118 time=10.5 ms
64 bytes from 8.8.8.8: icmp_seq=36 ttl=118 time=116 ms
64 bytes from 8.8.8.8: icmp_seq=38 ttl=118 time=112 ms
64 bytes from 8.8.8.8: icmp_seq=39 ttl=118 time=108 ms
64 bytes from 8.8.8.8: icmp_seq=40 ttl=118 time=231 ms
64 bytes from 8.8.8.8: icmp_seq=41 ttl=118 time=24.0 ms
64 bytes from 8.8.8.8: icmp_seq=42 ttl=118 time=28.2 ms
64 bytes from 8.8.8.8: icmp_seq=43 ttl=118 time=32.0 ms
64 bytes from 8.8.8.8: icmp_seq=44 ttl=118 time=140 ms
64 bytes from 8.8.8.8: icmp_seq=45 ttl=118 time=146 ms
64 bytes from 8.8.8.8: icmp_seq=46 ttl=118 time=47.6 ms
64 bytes from 8.8.8.8: icmp_seq=47 ttl=118 time=52.0 ms
64 bytes from 8.8.8.8: icmp_seq=48 ttl=118 time=57.1 ms
64 bytes from 8.8.8.8: icmp_seq=49 ttl=118 time=60.9 ms
64 bytes from 8.8.8.8: icmp_seq=50 ttl=118 time=67.0 ms
64 bytes from 8.8.8.8: icmp_seq=51 ttl=118 time=3.90 ms
64 bytes from 8.8.8.8: icmp_seq=52 ttl=118 time=20.3 ms
64 bytes from 8.8.8.8: icmp_seq=53 ttl=118 time=4.81 ms
64 bytes from 8.8.8.8: icmp_seq=54 ttl=118 time=87.0 ms
64 bytes from 8.8.8.8: icmp_seq=55 ttl=118 time=92.9 ms
64 bytes from 8.8.8.8: icmp_seq=56 ttl=118 time=200 ms
64 bytes from 8.8.8.8: icmp_seq=57 ttl=118 time=4.52 ms
64 bytes from 8.8.8.8: icmp_seq=58 ttl=118 time=5.47 ms
64 bytes from 8.8.8.8: icmp_seq=59 ttl=118 time=98.4 ms
64 bytes from 8.8.8.8: icmp_seq=61 ttl=118 time=120 ms
64 bytes from 8.8.8.8: icmp_seq=62 ttl=118 time=133 ms
64 bytes from 8.8.8.8: icmp_seq=63 ttl=118 time=128 ms
64 bytes from 8.8.8.8: icmp_seq=64 ttl=118 time=235 ms
64 bytes from 8.8.8.8: icmp_seq=65 ttl=118 time=30.6 ms
64 bytes from 8.8.8.8: icmp_seq=66 ttl=118 time=139 ms
64 bytes from 8.8.8.8: icmp_seq=67 ttl=118 time=245 ms
64 bytes from 8.8.8.8: icmp_seq=68 ttl=118 time=41.3 ms
64 bytes from 8.8.8.8: icmp_seq=69 ttl=118 time=138 ms
64 bytes from 8.8.8.8: icmp_seq=70 ttl=118 time=253 ms
64 bytes from 8.8.8.8: icmp_seq=71 ttl=118 time=47.8 ms
64 bytes from 8.8.8.8: icmp_seq=72 ttl=118 time=51.9 ms
64 bytes from 8.8.8.8: icmp_seq=73 ttl=118 time=56.8 ms
64 bytes from 8.8.8.8: icmp_seq=74 ttl=118 time=62.3 ms
64 bytes from 8.8.8.8: icmp_seq=75 ttl=118 time=67.8 ms
64 bytes from 8.8.8.8: icmp_seq=76 ttl=118 time=206 ms
64 bytes from 8.8.8.8: icmp_seq=77 ttl=118 time=4.67 ms
64 bytes from 8.8.8.8: icmp_seq=78 ttl=118 time=148 ms
64 bytes from 8.8.8.8: icmp_seq=79 ttl=118 time=207 ms
64 bytes from 8.8.8.8: icmp_seq=80 ttl=118 time=3.99 ms
64 bytes from 8.8.8.8: icmp_seq=81 ttl=118 time=4.59 ms
64 bytes from 8.8.8.8: icmp_seq=82 ttl=118 time=38.8 ms
64 bytes from 8.8.8.8: icmp_seq=83 ttl=118 time=4.59 ms
64 bytes from 8.8.8.8: icmp_seq=84 ttl=118 time=82.3 ms
64 bytes from 8.8.8.8: icmp_seq=85 ttl=118 time=105 ms
64 bytes from 8.8.8.8: icmp_seq=86 ttl=118 time=54.2 ms
64 bytes from 8.8.8.8: icmp_seq=87 ttl=118 time=15.2 ms
64 bytes from 8.8.8.8: icmp_seq=88 ttl=118 time=4.62 ms
64 bytes from 8.8.8.8: icmp_seq=89 ttl=118 time=104 ms
64 bytes from 8.8.8.8: icmp_seq=90 ttl=118 time=69.6 ms
64 bytes from 8.8.8.8: icmp_seq=91 ttl=118 time=28.3 ms
64 bytes from 8.8.8.8: icmp_seq=92 ttl=118 time=6.45 ms
64 bytes from 8.8.8.8: icmp_seq=93 ttl=118 time=113 ms
64 bytes from 8.8.8.8: icmp_seq=94 ttl=118 time=77.2 ms
64 bytes from 8.8.8.8: icmp_seq=95 ttl=118 time=38.4 ms
64 bytes from 8.8.8.8: icmp_seq=96 ttl=118 time=6.64 ms
64 bytes from 8.8.8.8: icmp_seq=97 ttl=118 time=120 ms
64 bytes from 8.8.8.8: icmp_seq=98 ttl=118 time=60.1 ms
64 bytes from 8.8.8.8: icmp_seq=99 ttl=118 time=155 ms
64 bytes from 8.8.8.8: icmp_seq=100 ttl=118 time=107 ms
64 bytes from 8.8.8.8: icmp_seq=101 ttl=118 time=56.9 ms
64 bytes from 8.8.8.8: icmp_seq=102 ttl=118 time=14.3 ms
64 bytes from 8.8.8.8: icmp_seq=103 ttl=118 time=5.59 ms
64 bytes from 8.8.8.8: icmp_seq=104 ttl=118 time=4.53 ms
64 bytes from 8.8.8.8: icmp_seq=105 ttl=118 time=117 ms
64 bytes from 8.8.8.8: icmp_seq=106 ttl=118 time=4.51 ms
64 bytes from 8.8.8.8: icmp_seq=107 ttl=118 time=4.54 ms
64 bytes from 8.8.8.8: icmp_seq=108 ttl=118 time=150 ms
64 bytes from 8.8.8.8: icmp_seq=109 ttl=118 time=5.36 ms
64 bytes from 8.8.8.8: icmp_seq=110 ttl=118 time=10.1 ms
64 bytes from 8.8.8.8: icmp_seq=111 ttl=118 time=32.2 ms
64 bytes from 8.8.8.8: icmp_seq=112 ttl=118 time=70.1 ms
64 bytes from 8.8.8.8: icmp_seq=113 ttl=118 time=23.4 ms
64 bytes from 8.8.8.8: icmp_seq=114 ttl=118 time=4.57 ms
64 bytes from 8.8.8.8: icmp_seq=115 ttl=118 time=122 ms
64 bytes from 8.8.8.8: icmp_seq=116 ttl=118 time=84.8 ms
64 bytes from 8.8.8.8: icmp_seq=117 ttl=118 time=45.8 ms
64 bytes from 8.8.8.8: icmp_seq=118 ttl=118 time=7.48 ms
64 bytes from 8.8.8.8: icmp_seq=119 ttl=118 time=4.42 ms
^C
--- 8.8.8.8 ping statistics ---
119 packets transmitted, 116 received, 2.52101% packet loss, time 23754ms
rtt min/avg/max/mdev = 3.624/70.204/305.533/64.207 ms, pipe 2

RE: RTL8922AE: Severe latency spikes (>200ms) during wifi scan triggers

[Ping-Ke Shih]

Sivanantham Chinnaiyan <sivananth321@gmail.com> wrote:
> Severe latency spikes (200ms+) occur whenever a Wi-Fi scan is
> triggered (e.g., clicking Wi-Fi menu in GUI). This happens
> consistently on both 2.4 GHz and 5 GHz networks, though it is much
> more evident in 2.4GHz channel. I know that latency spikes during
> scans are normal. But I am not sure if 150+ms is considered normal.

It seems like the ping latency without scanning is about 50ms in your
environment, and currently off-channel time of RTL8922AE is 100ms, so
roughly it'd be 150ms with scanning.

What is the problem you are encountering because of long latency?

Ping-Ke

Re: RTL8922AE: Severe latency spikes (>200ms) during wifi scan triggers

[Sivanantham Chinnaiyan]

> It seems like the ping latency without scanning is about 50ms in your
> environment, and currently off-channel time of RTL8922AE is 100ms, so
> roughly it'd be 150ms with scanning.

Got it. Thanks for the clarification.

> What is the problem you are encountering because of long latency?

I encountered disconnects / lags during video calls with the previous
kernel versions. But it seems to be stable from the kernel version
6.19.13 which is what I am currently using. So I wanted to check with
you if this can be reduced.