binding_refresh_interval not having any impact

[bapowell]

Running on a Raspberry Pi, NiceGUI is fairly CPU intensive (although still usable). I tried changing the binding_refresh_interval value, via a ui.run() parameter, but it doesn't seem to make any difference on CPU usage.

[falkoschindler]

As far as I can tell, binding_refresh_interval does have an effect. Adding a print statement within the loop() in binding.py demonstrates the impact of that interval. I tried it with the following example:

from nicegui import ui

class Model:
    def __init__(self):
        self.x = 1

model = Model()
ui.number('x').bind_value_from(model, 'x')

ui.run(binding_refresh_interval=0.5)

There is probably something else CPU-intensive going on in your code. Can you boil it down to some minimum example?

[bapowell]

I think what I'm seeing is essentially the minimum CPU usage from NiceGUI. In other words, using your very minimal example, I see roughly 50% CPU usage on one of the RPi's cores. Changing the binding_refresh_interval has no impact.

What's interesting is that I can run JustPy, using the example at the end of https://justpy.io/tutorial/model_and_data/, which is also doing bind operations, and it runs with less than 5% CPU usage on one core.

Please understand this isn't a knock against NiceGUI, since it has a much more "batteries included" approach, which I can appreciate. But a 10x increase in CPU usage seems excessive, and I wonder if there's something I'm missing.

[rodja]

We will run our examples on an RPi in the next days and come back to you.

[me21]

I'm running my nicegui on the Beaglebone Black single board computer, it has one CPU core and it uses 20% give or take.
During startup, it loads CPU fully, but I can live with that.

[falkoschindler]

I just checked the CPU usage on a Raspberry Pi 3 Model B V1.2 (2015) with a simple hello-world script:

from nicegui import ui

ui.label('Hello world!')

ui.run()

Here are my conclusions:

• reload=True (the default) can be costly. Here is a related discussion over at uvicorn: High CPU usage when using --reload encode/uvicorn#338. If in doubt, try using reload=False.
• It might also help to limit the amount of files that need to be watched: Originally I tested with a test script in my home folder. This causes uvicorn to watch the whole home directory ramping the CPU up to 100 %. After moving the script into a separate folder, uvicorn had to watch only a single file, lowering the CPU to less than 1 %.
• binding_refresh_interval does not have any significant impact for this tiny script.

So if you don't need auto-reload, set it to False. Otherwise, keep the watched directory small (and/or use reload_includes, reload_excludes and reload_dirs).

Note that changes to the arguments of ui.run are not caught by the auto-reload but require restarting the script completely.

[bapowell]

You nailed it, @falkoschindler.

I had my venv in the same folder as my test script. Changing reload to False lowered CPU to around 1%, as did moving the script to its own folder (keeping reload=True).

[me21]

In my case, running it on Beaglebone Black, changing refresh interval from 0.1 to 0.5 lowered CPU load from 60% to 10% approximately.
So on weaker CPU it does matter too.

I mean I ran my large script for UI, not the "hello world" script.