User`s guide

7 Models with Multiple Sample Rates
7-10
See “Multitasking and Pseudomultitasking” on page 7–5 for a description of
how this works. It is important to understand that section before proceeding
here.
Multitasking Operation
The use of multitasking can improve the efficiency of your program if the model
is large and has many blocks executing at each rate. It can also degrade
performance if your model is dominated by a single rate, and only a few blocks
execute at a slower rate. In this situation, the overhead incurred in task
switching can be greater than the time required to execute the slower blocks.
It is more efficient to execute all blocks at the dominant rate.
If you have a model that can benefit from multitasking execution, you may
need to modify your Simulink model for this scheme to generate correct results.
Singletasking Operation
Alternatively, you can run your real-time program in singletasking mode.
Singletasking programs require longer sample intervals due to the inherent
inefficiency of that mode of execution.