Why does sample time propagation take 10-20 minutes in newer Matlab Simulink Version?

We use Simulink for large system simulations with multiple C-Mex S-Functions inside.

Right now we want to upgrade to Matlab 2024a. However when testing our models with Matlab 2023b and 2024a, we noticed that starting a simulation in Normal Mode takes ~20 minutes, while before it took at most 1-2 Minutes.

Same behaviour for Accelerator Mode, where it easily takes half an hour until the simulation start (before ~5-10 minutes) and even worse for exporting our Models to FMU.

During the compile process of the model we observe "Compiling: Propagating sample times" to take a lot longer than before.

What has changed in the latest Simulink releases, that sample time propagation now takes way longer than before?

We already tried looking at settings but couldn't find anything new that seems to change anything here. We also tried setting explicit sample times whereever possible etc..

What else can we do to get to the root of the problem, or is this just something that new Simulink Versions have inside now?

[Fangjun Jiang]

I wonder if those S-functions have been re-built in the newer version of MATLAB. If Yes, I would suggest sending the models to the Mathworks to find the cause.

[Daniel Eberle]

Thank you for the comment, yes indeed we re-built it in the newer versions.

I was hoping maybe someone else experienced this behaviour, but I guess I will contact support directly then.