Testing rtw_8822bu, feed back. (Slow bitrate)

[WallyZambotti]

Testing rtw_8822bu, feed back. (Slow bitrate)

[dubhater]

Thank you for your detailed report. Something is still wrong with this chip. Unfortunately I don't have a device to test.

[morrownr]

@dubhater

I have several usb wifi adapters based on the rtl8812bu chip. We can worry about how to put one in your hands as we have time but for now, tell me what you want me to do.

FYI: I've been sick this week. Am starting to feel a little better now.

[morrownr]

@dubhater

Afterthought: The rtl8812bu chip is likely the most popular Realtek chip in the hands of Linux users so it is a priority...once rtw_8821au and rtw_8812au have gone in.

[morrownr]

@dubhater

Test system:
x86_64
Debian 12
kernel 6.6
AP: 80 MHz channel width and supports WiFi 5 (actuall it supports WiFi 6 but this adapter in question can't do WiFi 6).
Channel 100 (DFS) clean air
signal level of -25 dBm, through 2 walls and about 6 meters distance
Adapter: rtl8812bu based running as client, managed mode
Driver: rtw_8822bu

Here are two runs with iperf3:

$ iperf3 -c 192.168.1.1
Connecting to host 192.168.1.1, port 5201
[  5] local 192.168.1.135 port 35716 connected to 192.168.1.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  69.6 MBytes   584 Mbits/sec    0    976 KBytes       
[  5]   1.00-2.00   sec  67.5 MBytes   566 Mbits/sec    0    976 KBytes       
[  5]   2.00-3.00   sec  67.5 MBytes   566 Mbits/sec    0    976 KBytes       
[  5]   3.00-4.00   sec  66.2 MBytes   555 Mbits/sec    0    976 KBytes       
[  5]   4.00-5.00   sec  66.2 MBytes   556 Mbits/sec    0    976 KBytes       
[  5]   5.00-6.00   sec  67.5 MBytes   566 Mbits/sec    0    976 KBytes       
[  5]   6.00-7.00   sec  66.2 MBytes   556 Mbits/sec    0    976 KBytes       
[  5]   7.00-8.00   sec  68.8 MBytes   577 Mbits/sec    0    976 KBytes       
[  5]   8.00-9.00   sec  67.5 MBytes   566 Mbits/sec    0    976 KBytes       
[  5]   9.00-10.00  sec  66.2 MBytes   556 Mbits/sec    0    976 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   673 MBytes   565 Mbits/sec    0             sender
[  5]   0.00-10.01  sec   671 MBytes   563 Mbits/sec                  receiver

$ iperf3 -c 192.168.1.1 -R
Connecting to host 192.168.1.1, port 5201
Reverse mode, remote host 192.168.1.1 is sending
[  5] local 192.168.1.135 port 39732 connected to 192.168.1.1 port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  35.0 MBytes   293 Mbits/sec                  
[  5]   1.00-2.00   sec  7.04 MBytes  59.0 Mbits/sec                  
[  5]   2.00-3.00   sec  7.61 MBytes  63.9 Mbits/sec                  
[  5]   3.00-4.00   sec  7.53 MBytes  63.2 Mbits/sec                  
[  5]   4.00-5.00   sec  7.56 MBytes  63.5 Mbits/sec                  
[  5]   5.00-6.00   sec  6.06 MBytes  50.8 Mbits/sec                  
[  5]   6.00-7.00   sec  7.50 MBytes  62.9 Mbits/sec                  
[  5]   7.00-8.00   sec  7.48 MBytes  62.7 Mbits/sec                  
[  5]   8.00-9.00   sec  7.39 MBytes  62.0 Mbits/sec                  
[  5]   9.00-10.00  sec  7.59 MBytes  63.7 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.11  sec   103 MBytes  85.1 Mbits/sec   24             sender
[  5]   0.00-10.00  sec   101 MBytes  84.5 Mbits/sec                  receiver

Quick conclusion: Slow bitrate is only in one direction. Hopefully that is enough to help you know where to start looking. Let me know what specific tests to run.

@WallyZambotti

$ iwconfig

That is a very old unsupported command. Recommend you discontinue use. Tell us what you want to do and we can recommend modern supported commands. You can start with iw.

[dubhater]

@morrownr Something to check is the TX and RX rates in wavemon when you see the low speed with iperf3.

[morrownr]

@dubhater

$ iperf3 -c 192.168.1.1

wavemon shows: rx rate: 86 Mbps, tx rate: 866 Mbps while iperf3 is running.

$ iperf3 -c 192.168.1.1
Connecting to host 192.168.1.1, port 5201
[  5] local 192.168.1.135 port 59808 connected to 192.168.1.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  71.1 MBytes   597 Mbits/sec    0    974 KBytes       
[  5]   1.00-2.00   sec  66.2 MBytes   556 Mbits/sec    0    974 KBytes       
[  5]   2.00-3.00   sec  68.8 MBytes   577 Mbits/sec    0    974 KBytes       
[  5]   3.00-4.00   sec  66.2 MBytes   556 Mbits/sec    0    974 KBytes       
[  5]   4.00-5.00   sec  67.5 MBytes   566 Mbits/sec    0    974 KBytes       
[  5]   5.00-6.00   sec  66.2 MBytes   556 Mbits/sec    0    974 KBytes       
[  5]   6.00-7.00   sec  67.5 MBytes   566 Mbits/sec    0    974 KBytes       
[  5]   7.00-8.00   sec  67.5 MBytes   566 Mbits/sec    0    974 KBytes       
[  5]   8.00-9.00   sec  66.2 MBytes   556 Mbits/sec    0    974 KBytes       
[  5]   9.00-10.00  sec  67.5 MBytes   566 Mbits/sec    0    974 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   675 MBytes   566 Mbits/sec    0             sender
[  5]   0.00-10.01  sec   672 MBytes   563 Mbits/sec                  receiver

---

$ iperf3 -c 192.168.1.1 -R

wavemon shows: rx rate: 19 Mbps, tx rate: 866 Mbps while iperf3 is running.

$ iperf3 -c 192.168.1.1 -R
Connecting to host 192.168.1.1, port 5201
Reverse mode, remote host 192.168.1.1 is sending
[  5] local 192.168.1.135 port 36470 connected to 192.168.1.1 port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  28.9 MBytes   243 Mbits/sec                  
[  5]   1.00-2.00   sec  4.91 MBytes  41.2 Mbits/sec                  
[  5]   2.00-3.00   sec  7.07 MBytes  59.3 Mbits/sec                  
[  5]   3.00-4.00   sec  7.51 MBytes  63.0 Mbits/sec                  
[  5]   4.00-5.00   sec  7.49 MBytes  62.8 Mbits/sec                  
[  5]   5.00-6.00   sec  7.52 MBytes  63.1 Mbits/sec                  
[  5]   6.00-7.00   sec  7.66 MBytes  64.3 Mbits/sec                  
[  5]   7.00-8.00   sec  7.40 MBytes  62.1 Mbits/sec                  
[  5]   8.00-9.00   sec  7.63 MBytes  64.0 Mbits/sec                  
[  5]   9.00-10.00  sec  7.59 MBytes  63.6 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  95.0 MBytes  79.7 Mbits/sec  134             sender
[  5]   0.00-10.00  sec  93.7 MBytes  78.6 Mbits/sec                  receiver

[Samt43]

@morrownr @dubhater : i'm also noticing slow bandwith using 8822bu.
Connecting to host 10.0.0.1, port 5201
[ 5] local 100.115.92.198 port 60874 connected to 10.0.0.1 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 6.27 MBytes 52.6 Mbits/sec 3 211 KBytes
[ 5] 1.00-2.00 sec 9.13 MBytes 76.6 Mbits/sec 0 242 KBytes
[ 5] 2.00-3.00 sec 8.82 MBytes 74.0 Mbits/sec 1 266 KBytes
[ 5] 3.00-4.00 sec 8.70 MBytes 73.0 Mbits/sec 0 290 KBytes
[ 5] 4.00-5.00 sec 5.78 MBytes 48.5 Mbits/sec 2 235 KBytes
[ 5] 5.00-6.00 sec 9.13 MBytes 76.6 Mbits/sec 0 264 KBytes
[ 5] 6.00-7.00 sec 9.45 MBytes 79.2 Mbits/sec 0 280 KBytes
[ 5] 7.00-8.03 sec 11.8 MBytes 95.6 Mbits/sec 0 307 KBytes
[ 5] 8.03-9.00 sec 10.9 MBytes 94.3 Mbits/sec 0 334 KBytes
[ 5] 9.00-10.00 sec 10.4 MBytes 87.0 Mbits/sec 2 355 KBytes

---

[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 90.3 MBytes 75.8 Mbits/sec 8 sender
[ 5] 0.00-10.04 sec 89.7 MBytes 75.0 Mbits/sec receiver

iperf Done.

[WallyZambotti]

Bitrate continues to degrade over time:

$ iw wlxbcec4322ff20 link
Connected to 74:83:c2:b5:56:ca (on wlxbcec4322ff20)
SSID: TCS
freq: 5200
RX: 12596516 bytes (52511 packets)
TX: 558933 bytes (3372 packets)
signal: -48 dBm
rx bitrate: 65.0 MBit/s VHT-MCS 7 VHT-NSS 1
tx bitrate: 135.0 MBit/s VHT-MCS 7 40MHz VHT-NSS 1

bss flags:	short-slot-time
dtim period:	3
beacon int:	100

[misha4gps]

Drivers comparison in AP mode:

88x2bu (morrownr)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-60.00  sec  1.21 GBytes   173 Mbits/sec                  receiver
iperf3: the client has terminated
-----------------------------------------------------------

rtw_8822bu (lwfinger):
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-30.00  sec   538 MBytes   150 Mbits/sec                  receiver
iperf3: the client has terminated
-----------------------------------------------------------

rtw88_8822bu (kernel)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-35.00  sec   121 MBytes  29.0 Mbits/sec                  receiver
iperf3: the client has terminated
-----------------------------------------------------------

Hardware:

Bus 001 Device 004: ID 0bda:b82c Realtek Semiconductor Corp. 802.11ac NIC (rtl8822bu)

Kernel:

Linux Workstation 6.10.0-rc7+ #5 SMP PREEMPT_DYNAMIC Fri Jul 19 20:42:15 EEST 2024 x86_64 x86_64 x86_64 GNU/Linux

Successful test of 802.11r:

88x2bu  - no
rtw_8822bu  - yes
rtw88_8822bu  - yes

Questions:

1. What is the main reason for the rtw88_8822bu driver being so slow?
2. Why is the rtw_8822bu driver slower than 88x2bu ?

[morrownr]

@misha4gps

What is the main reason for the rtw88_8822bu driver being so slow?

Probably the following is largely the cause:

[1/4] wifi: rtw88: Init RX burst length for 8822cu/8822bu/8821cu

You can find that patch series at:

https://patchwork.kernel.org/project/linux-wireless/list/

It was sent in yesterday by Dubhater. My opinion is that Realtek did not do a very good job with rtw88 and they included no support for USB. That has all come from the community. By the time we see kernel 6.12 released, you should see better performance with rtw88_8822bu and the other drivers in rtw88.

Why is the rtw_8822bu driver slower than 88x2bu ?

Dubhater can certainly answer this better than me but I'd rather keep him busy prepping patches for upstreaming the numerous patches that need to go upstream such as for the new rtl8821au and rtl8812au drivers. It is a lot of work.

While performance for rtw_8822bu is currently much better than rtw88_8822bu, performance is not symmetrical as shown in the last iperf3 testing I posted above. Why that is is not known to me at this time but if anyone can get to the bottom of it, Dubhater can we need to allow him time to get all of the patches that need to go upstream on their way right now and then we can make a plan and start gathering information. This project covers a lot of drivers and it is complicated work. It will be very nice to see the many patches that are going into 6.12 in place so we can begin the process if depreciating the Reaktek out-of-kernel drivers.

[misha4gps]

@morrownr
Thanks for the link and explanation.
and many thanks to Dubhater for his efforts in improving the driver

[morrownr]

@misha4gps

Let me make sure I did not mislead you. Any patches that have gone in to go into the kernel are already in this repo. You can look at that patch series right here.

[misha4gps]

@morrownr,
I understand this and that is why i did the test.

[WallyZambotti]

Not sure if the following information is at all relevant.

The laptop that I was testing the rtl8822bu just happened to have a PCI rtl8822ce for its Wifi adapter.

When I use iw link it shows the RX bit rate is 175 but the TX bit rate is 600. I would rather that be the other way around but there may be a wider issue with the rtl driver.

[henkv1]

When I use rtw88 as an AP, my client reports a rx bitrate of 6.0MBit/s, tx bitrate is 390.0 MBit/s.
It makes no difference if I use my 8811cu or my 8812bu adapter as AP. My client uses an Intel wireless adapter. The AP is a Raspberry Pi 3b running 64bit Arch.

[WallyZambotti]

From my testing it appears to drop under load. So the bit rate may start at 216 or higher but immediately after placing a load it will drop to 39. And when the load stops the bit rate will rise back up. Even when there is only a load on transmission the RX rate will drop. But only the RX bit rate will change. The TX seems completely steady.

[likknb]

yes,help the question please 。rtw88_8822cs According to the same situation