MantaFlow CPU usage

I’m on a 8 core machine and I only get 37 % CPU usage when backing MantaFlow data, is there any setting that let me use all cores?

You use a CPU monitor that tells you the CPU usage thread by thread, preferably graphically indicated. Surely this is multicore in your machine, but each thread does not work in good percentage apparently.
Not sure how your simulation setup is. Here on Linux testing with default cube and Object > Quick Effects > Quick Liquid (Resolution Divisions=256). This is multicore. Bake Data constantly working on each thread at an average of 65%. Bake Mesh working at 100% mostly, with small periodic intervals where it is reduced to 10%.

I tested on both macOS and Windows. I get almost a 100% on Rendering, so I guess multi treating is not used.

Well, I don’t know what to say. You did not share your scene so we can test if it is your simulation settings.

We could stop guessing things if you at least get a CPU monitor that shows the information thread by thread, and no global CPU usage. Something like this:

Does MacOS not have such a system monitor? If you get it, you share a screenshot of the system monitor while it is open and after baking the simulation for a few seconds.

Sure it has, just didn’t understood your question.
Here you see all threats (8 core)

I get almost 99% on all when rendering with Cycles.

I think the read n write process may have something to do aslo…?
If it could use GPU +CPU in the future???

You seem to have suggested that because that global CPU usage percentage, mantaflow is not working on all threads. I say, that’s weird because Mantaflow is multi-threaded in Blender. Also, showing a global percentage of CPU usage does not give much information about whether the job is working on a single thread or on all threads. That’s why I asked you to use some CPU monitor that shows the work on all threads.
Regarding cycles, yes, it works at almost 100% in all threads. But simulation is a very different task. You will see in Blender that simulations have multi-threaded implementation, but most of the time complex simulations will not work at more than 65% on average.

So if your simulation is really working with a single thread, I think you should report the problem by sharing the .blend file with developers.
If this is working on all threads but at a low percentage of CPU usage constantly (a value not exceeding 37%, for example), you should also report the problem by sharing the .blend file so developers can see what the problem could be regarding that multi-thread low performance.

I also asked you if you can share the .blend file here so that other users can test it.

Well, hard to find out. I have to run another test on Windows, but meanwhile,
here is the file, simple fluid setup:
liquid.blend (637.8 KB)

Here how the simulation works on my machine (Linux - i7-3770):

*Bake Data:

Working multi-thread. Apparently one thread is reserved for a special task and running almost 100% continuously. The rest of the threads constantly working at an average of 65%

*Bake Mesh:

Working multi-thread. Working at an average of 60%, with valleys of approximately 30% and peaks of 80% on average.