Quetions about the task scheduler

[aggarg (Gaurav Aggarwal)]

@Yueming

In my humble opinion, searching the highest priority task in the whole pxReadyTasksLists everytime only sacrifices a little bit performance. If a MCU vendor cares about the performance, they should implement their own optimised task selection.

uxTopReadyPriority records the highest priority for which a task is ready to run. It is updated whenever a task is added to ready list: https://github.com/FreeRTOS/FreeRTOS-Kernel/blob/main/tasks.c#L223. This way the scheduler does not need to search for the all the ready lists but only the list for uxTopReadyPriority.
Port optimized task selection usually maintain top ready priority as a bit in a 32-bit number and use a hardware instruction to find the topmost set bit: https://github.com/FreeRTOS/FreeRTOS-Kernel/blob/main/portable/GCC/ARM_CM4F/portmacro.h#L132. It is not yet clear how setting uxTopReadyPriority can cause any problem.

If you are using Cortex-M33, is there a reason not to use the official port: https://github.com/FreeRTOS/FreeRTOS-Kernel/tree/main/portable/GCC/ARM_CM33.

Thanks.