how do we compare uc/OS with freeRTOS. I am interested only in reliability and performance. ie how good is the existing features of freeRTOS compared to the similar features offered by uc/OS

Which is best depends on your application. The mechanics of using FreeRTOS and uCOS are very similar.

There are two main differences between the two:

1)Licensing. FreeRTOS is completely free for any application. The uCOS source code comes bundled with a book requiring purchase, and a binary run time license ($$$) is required if you use uCOS in a commercial application.

2)Scheduling. uCOS uses a bitmap scheduler, FreeRTOS does not. A bitmap scheduler has the advantage of allowing a more deterministic context switch time, and in some cases a faster context switch time – it does however severely restrict your design freedom as it only allows a single task at any given priority level. FreeRTOS on the other hand is more flexible as any number of tasks can share the same priority.

I think FreeRTOS is simpler to use; initialization is automatic on creation of the first task, and ISR routines don’t have to be written in assembler. But you are probably asking the wrong person if you want a non-biased opinion!

Regards.

another point is ports: ucos supports tens (hundreds) of MCUs while freertos is still starting up. also code quality has been proven by validation suites for ucos (e.g. FDA).

I wonder how well freertos covers a full range testsuite..?