High CPU usage when using --reload

Using the example code

async def app(scope, receive, send):
    assert scope['type'] == 'http'

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            [b'content-type', b'text/plain'],
        ],
    })
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',
    })

and running uvicorn main:app, CPU usage is unnoticeable (less than 1% of 1 core). But when running with uvicorn main:app --reload, CPU usage jumps to 54% of 1 core.

Environment: python -V: Python 3.7.2 uvicorn: 0.6.1 uname -a: Linux architect 5.0.4-arch1-1-ARCH #1 SMP PREEMPT Sat Mar 23 21:00:33 UTC 2019 x86_64 GNU/Linux

[kevchentw]

I found that there are --reload-dir settings already. By applying app folder, CPU usage significant decrease.

[uSpike]

I had this issue with my project.

With only --reload, it was eating up 25% of a 4 core CPU watching 8135 files in my venv/ folder.

By adding --reload-dir src/ where src/ contains my application, the CPU issue went away completely.

Maybe a decent solution is to have uvicorn ignore common virtualenv directory names, like venv/ .venv/, etc?