High idle CPU usage with Django Channels WebSockets (asyncio._run_once / await_many_dispatch hot

[JaeHyuckSa]

Hi,

I'm using Django Channels for WebSocket connections and I'm seeing what looks like
a CPU bottleneck in the event loop / Channels dispatch layer, even when the
connections are basically idle.

Environment

• Python: 3.13.5
• Django: 5.2.8
• channels: 4.3.2
• channels-redis: 4.3.0
• ASGI server: uvicorn 0.38.0
• Channel layer: Redis

Symptom

When I just keep WebSocket connections open (no heavy messages being sent),
the CPU usage of a single worker process keeps growing over time.
Roughly speaking, CPU usage increases by about 0.1% per second for that worker,
even though the app is not doing any significant work at the application level.

To understand what’s going on, I profiled the process and got this summary
(only the top part is shown here):

GIL: 92.00%, Active: 104.00%, Threads: 9

%Own   %Total  OwnTime  TotalTime  Function (filename)
9.00%  92.00%   10.05s    85.75s   _run_once (asyncio/base_events.py)
9.00%  80.00%    9.23s    73.42s   _run (asyncio/events.py)
12.00%  13.00%    7.88s     9.60s   _wait (asyncio/tasks.py)
7.00%  59.00%    6.07s    54.17s   await_many_dispatch (channels/utils.py)
5.00%  11.00%    5.31s     9.13s   create_task (asyncio/base_events.py)
6.00%  28.00%    4.61s    21.55s   wait (asyncio/tasks.py)
2.00%   8.00%    3.91s     9.97s   dispatch (channels/consumer.py)
2.00%  10.00%    3.84s    13.81s   dispatch (websocket_django_common/consumers.py)
...
0.00%  92.00%    0.84s    86.59s   run_forever (asyncio/base_events.py)
0.00%  61.00%    0.07s    55.74s   run_asgi (uvicorn/protocols/websockets/websockets_impl.py)
0.00%  61.00%    0.30s    55.59s   __call__ (channels/routing.py)
0.00%  61.00%    0.17s    55.41s   __call__ (websocket_django_common/middlewares.py)
0.00%  59.00%    0.16s    54.41s   app (channels/consumer.py)

[carltongibson]

@JaeHyuckSa Please don't cross post. This is a duplicate of your issue on the Forum.

[JaeHyuckSa]

My sincere apologies — I had overlooked that detail. I will proceed to close this issue.