High Interrupt Jitter on R5 (MPSoC)

Some time later, including the Easter vacations, i came back to this problem:

I have tried to force the ISR into the TCM, including the interrupt stack. I must admit that I’m not entirely convinced that I’ve found every part of the stack in FreeRTOS, but I think most of it is covered.
Unfortunately, this does not solve the problem. It gets a little better, but not significantly.
But in the relatively short test I never observe a missing interrupt, only the jitter remains.

One other thing FreeRTOS adds is the recurring timer interrupt for the system tick. I wonder if one of the bus transactions interacting with the timer is stalling the R5 briefly. Maybe that bus isn’t configured to be as fast as it should be, or maybe another peripheral on that bus is having its own transaction (maybe with the application CPU?), etc.

I can’t think of any other differences between the bare-metal and FreeRTOS implementations.

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