1. A comparison between FreeRTOS and RTLinux in embedded real-time systems

2. Comparison on Size FreeRTOS RTLinux Kernel Size Kernel Size
Few megabytes
RAM required
Over few megabytes
Kernel Size
About 4.4 kilobytes
RAM required
About 200 bytes

3. Platform support RTLinux FreeRTOS supports architectures like x86
much more complex (much due to the Linux kernel)
harder to port to new platforms.
FreeRTOS
smaller microcontrollers
Support a greater number of platforms
portable code
all kernel code is contained in just three files

4. Features and Scalability
RTLinux
Provide all the things that a normal Linux distribution can.
Down to ARM. Upwards to full grown "home computer systems".
FreeRTOS
Provide only basic features.
only some basic scheduling
inter-process communication (IPC)
semaphores for synchronization
Hard to scale beyond the target of the platform.

5. Scheduler RTLinux FreeRTOS
A simple insmod gives the possibility to change scheduler.
a basic highest priority first scheduler.
earliest deadline first
FreeRTOS
a highest priority first scheduler.
same priority tasks is given "fair" process time by round robin.