Extremely slow json.load of a network response in WSL

Question

Decoding a json response takes a lot of time on my system - Precision 5520 (11th gen I7, 64 GB) with Linux 20.04 LTS under WSL2 under Windows 10 Pro. Here is the relevant part of the code:

def ms_now():
    return int(time.time_ns() / 1000000)

class Timer():
    def __init__(self):
        self.start = ms_now()

    def stop(self):
        return ms_now() - self.start

timer = Timer()
response = client.invoke(
    FunctionName='my-aws-lambda-function',
    Payload=json.dumps({'body': texts}),
)
print("response", timer.stop(), flush=True)
payload_json = response['Payload']
print("payload_json", timer.stop(), flush=True)
result = json.load(payload_json)
print("result", timer.stop(), flush=True)

This code invokes an AWS Lambda function. The response consists of 38,400 floats. Here is an output of one run (the times are in milliseconds):

response 5619
payload_json 5620
result 76314

It takes more than a minute to deserialize that response which is not that large by any means. I ran this same code in the terminal of PythonAnywhere and the deserialization took 100 milliseconds.

I suspect that WSL is the culprit. How do I diagnose and fix this problem?

EDIT

1. The same script works fine in the Windows host:

response 1934
payload_json 1934
result 3239 

2. Since people seem to assume that it's my connection that's slow in WSL, note that when I install packages with large dependencies, such as HuggingFace's sentence-transformers, using pip, they are downloaded quite fast.

Answer 1

This problem is discussed in the bug-report Very slow network speed on WSL2 #4901, where no solution was found but many workarounds were listed. Below are some workarounds in reverse order of suggestion. One of them might perhaps pertain to your problem.

User denskh said :

Specifics of my case is slow upload speed on Win11/WSL2 ~3-4Mbps vs. download of ~500Mpbs. Enabling Netword Direct Memory Access on vEthernet (WSL) virtual adapter fixed this issue and brought upload speed to ~500Mpbs. To check current value run:

Get-NetAdapterAdvancedProperty -name "vEthernet (WSL)" -includehidden -DisplayName "Network Direct (RDMA)"

To enable:

Set-NetAdapterAdvancedProperty -name "vEthernet (WSL)" -includehidden -DisplayName "Network Direct (RDMA)" -DisplayValue "Enabled"

User Jean1995 remarked for WiFi :

My current workaround is to disable and re-enable "Allow other network users to connect through this computer's Internet connection" in the "Properties/Sharing" tab of my WLAN connection.

User sruester said :

Fixed it for me (Intel I219-V adapter with Intel drivers installed):

Properties of WSL ethernet adapter
   Configure ...
       Advanced
          "Large Send Offload Version 2 (IPv4)" -> Disabled
          "Large Send Offload Version 2 (IPv6)" -> Disabled

User eugepemi said :

Finally I tried to disable IPv6 from the vEthernet of WSL and in W11 doesn't appears listed in the control panels, reading GitHub I found out that is because is a hidden device, from PowerShell I managed to disable it and right now WSL is has regular network speeds, the command:

Disable-NetAdapterBinding -Name "vEthernet (WSL)" -ComponentID ms_tcpip6 -IncludeHidden

Some more workarounds can be found in the bug-report itself.