Hi Claudio,
Changing the execution mode between Parallel and Low-Latency won't actually make your model run any faster, it just affects whether the Primary Control Loop waits for the model loop(s) to finish. In Parallel mode, the model loops run in parallel with the PCL, which introduces a 1 tick delay but allows you to take better advantage of multicore systems. In Low-Latency mode, the models essentially run inside the PCL, which eliminates the 1 tick delay but causes the PCL to wait for models to complete before moving on. This is why you see the Model Count loop increase in Parallel mode, but the HP Count increase in Low-Latency mode. The cause for both is the same: your model is not able to complete in the 200 us (5 kHz) that you are trying to run your system at.
However, looking at your numbers, it seems like you are almost making the 5kHz rate, so there may be something you can do to squeeze out a bit of extra performance. Take a look at your BIOS settings on your computer and see whether there is anything you can disable that could increase your performance or reduce jitter (such as setting Legacy USB support to auto/disabled). You can also try switching between interrupt and polling mode for your network adaptor in Measurement and Automation Explorer.
It sounds like the CPU usage is primarily due to your one large model, with the rest of the system adding only a minimal amount of proccesing. This makes it difficult to move things around on the cores and realize any perfomance increases. If you are able to split your large model up into multiple smaller models (and map them together in System Explorer), you could then run different parts of the model on different cores and probably meet your desired 5kHz rate. This obviously will take some work by whoever created the model, but it may be worth it in order to take advantage of your quad core system.
Another possibility, if you want to keep it as one big model, may be to disable some of the cores on your system. Some processors will be able to take advantage of higher clock speeds if cores are disabled. For example, our PXIe-8133 controller, which has an Intel Core i7-820 processor, runs at 1.73 GHz on 4 cores. However, if you disable 2 of the cores in the BIOS you can run at 2.8 GHz, and moving down to a single core will yield a max 3.06 GHz. If your system is capable of something similar, you could maybe move down to 2 cores and have the PCL running on core 0 and your model running on core 1.
