Keil RTX v5 specific control block definitions (including sizes) as well as memory pool and message queue memory requirements are defined in the header file rtx_os.h:

If you provide memory for the RTOS objects, you need to know the size that is required for each object control block. The memory of the control block is provided by the parameter attr of the related osXxxxNew function. The element cb_mem is the memory address, cb_size is the size of the control block memory.

Refer to Static Object Memory for more information.

The following table lists the control block sizes:

Category	Control Block Size Attribute	Size	#define symbol
Thread Management	osThreadAttr_t::cb_mem	68 bytes	osRtxThreadCbSize
Timer Management	osTimerAttr_t::cb_mem	32 bytes	osRtxTimerCbSize
Event Flags	osEventFlagsAttr_t::cb_mem	16 bytes	osRtxEventFlagsCbSize
Mutex Management	osMutexAttr_t::cb_mem	28 bytes	osRtxMutexCbSize
Semaphores	osSemaphoreAttr_t::cb_mem	16 bytes	osRtxSemaphoreCbSize
Memory Pool	osMemoryPoolAttr_t::cb_mem	36 bytes	osRtxMemoryPoolCbSize
Message Queue	osMessageQueueAttr_t::cb_mem	52 bytes	osRtxMessageQueueCbSize