Re: [r8188eu] Worse performance with 5.15

["Schüll, Daniel" <daniel.schuell@fau.de>]

On 2022-01-29 04:55, Larry Finger wrote:
> On 1/28/22 16:13, Schüll, Daniel wrote:
>> 
>> After upgrading to the 5.15 kernel I noticed a drop in throughput when 
>> using my wifi dongle.
>> I'm using a TP-Link TL-WN725N-v2 (USB ID: 0bda:8179).
>> 
>> On the 5.15 kernel I was only able to get around 30 MBit/s in download 
>> (using google's speedtest).
>> After downgrading back to the 5.13 kernel I was back to 95 MBit/s I 
>> used to have (close to the max from my ISP).
>> 
>> A bit of research revealed, that you did a major overhaul of the 
>> r8188eu driver in 5.15.
>> I then compiled the old rtl8188eu driver from the 5.13 sources for 
>> 5.15, loaded it on 5.15 and was able to get 95 MBit/s again.
>> Finally I also tried the newest version of the new r8188eu driver 
>> (Commit fa78315452) on 5.15, but still only got 30 MBits/s.
>> All test used the same location of AP and dongle and were done 
>> multiple times, so influence from other wifi devices is negligible.
>> Seeing that the issue is fixable by using an other driver module on 
>> the same kernel, it seems very likely,
>> that the issue is in the driver and not in the setup or other kernel 
>> changes.
>> 
>> Is the throughput a known regression?
> 
> Daniel,
> 
> This throughput regression is not known to me. I have not been very
> involved with the changes being made to r8188eu, but I do test it
> regularly to ensure that it can still make a connection. With my
> tests, I do not recall getting a speed over 40-45 Mbps connecting to a
> local LibreSpeed instance connected to my AP via a 1 GHz wired line.
> As I recall, I never have gotten anything near 95 Mbps.
> 
> I generated a 5.13 kernel, and it did not get over 30 Mbps. I get the
> same download speed from Speedtest.net. As my up connection only runs
> at 12 Mbps, that is what I always get when using an external
> connection.

that's interesting. Can you confirm that you are using the 40 MHz 
frequency range?
My AP is an AVM FritzBox!3390. In its menu I can see that the wifi 
dongle is using the following configuration: 2.4 GHz, n, 40 MHz, WPA2, 1 
x 1
With the one antenna of the rtl8188eu and 40 MHz the theoretical limit 
is 150 Mbps.

I also retested with a local iperf server on the fritzbox.
This is where things get strange. With the new r8188eu driver iperf over 
TCP gives me ~60 Mbps.
While google's speedtest still gives me only ~30 Mbps (I also tested 
various other in-browser tests with same results).
With the old driver rtl8188eu again I get ~95 Mbps over iperf and 
in-browser.

Regards,
Daniel