MEMORY ALLOCATION IN REAL-TIME OPERATING SYSTEM

Memory allocation is even more critical in an RTOS than in other operating systems.
Firstly, speed of allocation is important. A standard memory allocation scheme scans a linked list of indeterminate length to find a suitable free memory block; however, this is unacceptable as memory allocation has to occur in a fixed time in an RTOS.
Secondly, memory can become fragmented as free regions become separated by regions that are in use. This can cause a program to stall, unable to get memory, even though there is theoretically enough available. Memory allocation algorithms that slowly accumulate fragmentation may work fine for desktop machines—when rebooted every month or so—but are unacceptable for embedded systems that often run for years without rebooting.
The simple fixed-size-blocks algorithm works astonishingly well for simple embedded systems.
Another real strength of fixed size blocks is for DSP systems particularly where one core is performing one section of the pipeline and the next section is being done on another core. In this case, fixed size buffer management with one core filling the buffers and another set of cores returning the buffers is very efficient. A DSP optimized RTOS like Unison Operating System or DSPnano RTOS provides these features.