zhengyushi(ZHENGYU SHI) <zhengyushi@xxxxxxxxxxxxxxxxxx> wrote:
>
> I’m seeing severe ping spikes (1?90 ms) when using the onboard Realtek RTL8851BE Wi-Fi (Device b851,
> rtw89_8851be) on Arch Linux. Switching to a USB-tethered phone (same AP) completely eliminates the jitter
> (<5 ms). The behavior is completely reproducible. I suspect an issue in the rtw89 driver’s power-management
> or PCIe handling.
>
> I tried
> - Disabling power management via injecting ASPM/L1/L1SS and CLKREQ via rtw89_pci.disable_clkreq=y
> rtw89_pci.disable_aspm_l1=y rtw89_pci.disable_aspm_l1ss=y
> - Verified no firmware‐driven roaming or reassociation in logs
>
> Device Info:
> % lspci | awk '/[Nn]et/ {print $1}' | xargs -i% lspci -ks %
> 07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8211/8411 PCI Express Gigabit
> Ethernet Controller (rev 15)
> DeviceName: Realtek RTL8125BG LAN
> Subsystem: ASUSTeK Computer Inc. Onboard RTL8111H Ethernet
> Kernel driver in use: r8169
> Kernel modules: r8169
> 08:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device b851
> Subsystem: AzureWave Device 6110
> Kernel driver in use: rtw89_8851be
> Kernel modules: rtw89_8851be
>
> % uname -r
> 6.14.4-arch1-1
>
> % mtr 8.8.8.8
> Apotheosis (192.168.0.42) → 8.8.8.8 (8.8.8.8) 2025-05-05T21:15:47+0800
> Host Loss% Snt Last Avg Best Wrst StDev
> 1. _gateway 0.3% 330 0.7 1.6 0.3 82.4 5.8
> 2. 100.66.0.3 1.2% 330 2.0 3.1 1.2 109.9 9.5
> 3. chj-dsl9.vqbn.com 0.3% 330 2.0 3.3 1.3 95.3 8.5
> 4. 132.147.112.109 0.0% 329 2.6 4.0 1.7 102.8 9.4
> 5. 132.147.112.194 24.0% 329 4.7 7.9 3.4 127.1 16.0
> 6. 209.85.255.97 0.0% 329 2.5 3.5 1.6 131.1 8.6
> 7. 142.251.241.1 0.0% 329 2.4 3.4 2.0 109.7 7.3
> 8. dns.google 0.0% 329 2.8 3.0 1.5 105.9 7.2
>
This is my test in office where at least 50 AP are existing:
(Actually I don't expect the latency is always low in this environment.)
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=3.40 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=24.0 ms
64 bytes from 192.168.0.1: icmp_seq=3 ttl=64 time=4.32 ms
64 bytes from 192.168.0.1: icmp_seq=4 ttl=64 time=4.36 ms
64 bytes from 192.168.0.1: icmp_seq=5 ttl=64 time=6.30 ms
64 bytes from 192.168.0.1: icmp_seq=6 ttl=64 time=7.15 ms
64 bytes from 192.168.0.1: icmp_seq=7 ttl=64 time=2.48 ms
64 bytes from 192.168.0.1: icmp_seq=8 ttl=64 time=2.54 ms
64 bytes from 192.168.0.1: icmp_seq=9 ttl=64 time=2.04 ms
64 bytes from 192.168.0.1: icmp_seq=10 ttl=64 time=122 ms
This is another test in my house where AP is much less:
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=2.86 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.33 ms
64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=1.31 ms
64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=3.54 ms
64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=1.50 ms
64 bytes from 192.168.1.1: icmp_seq=6 ttl=64 time=4.03 ms
64 bytes from 192.168.1.1: icmp_seq=7 ttl=64 time=3.55 ms
64 bytes from 192.168.1.1: icmp_seq=8 ttl=64 time=2.86 ms
64 bytes from 192.168.1.1: icmp_seq=9 ttl=64 time=1.27 ms
64 bytes from 192.168.1.1: icmp_seq=10 ttl=64 time=3.49 ms
I'm using firmware v0.29.41.3. Please check which version you are using.
Turning off power_save by 'sudo iw wlan0 set power_save off' can improve
a little bit. You can also try it.
The factors of high latency might be caused by noisy environment, so
RTL8851BE is hard to transmit out or collision. Using a sniffer with
ping test would be easier to diagnose the reason.
Method to use another RTL8851BE or other WiFi devices as a sniffer:
sudo iw dev wlan0 interface add mon0 type monitor
sudo wireshark
Then select proper channel via wireshark GUI to capture packets from/to
target RTL8851BE.
