Transcript Introduction to Real Time Systems

Memory Management
Akos Ledeczi
EECE 354, Fall 2012
Vanderbilt University
Memory Partitions
• Dynamic memory allocation
from the heap /malloc() and
free()/ can lead to memory
fragmentation
• µC/OS-III provides memory
partitions as an alternative
• Can create multiple
partitions with different
block sizes
Usage
OS_MEM MyPartition;
CPU_INT08U Storage[12][100];
/* malloc() also works */
void main()
{
…
OSMemCreate(&MyPartition, “My partition”,
(void *)&Storage[0][0],
12,100,
&err);
…
}
void MyTask(void *p_arg)
{
…
CPU_INT08U *block =
(CPU_INT08U *)OSMemGet(&MyPartition,&err);
if (err == OS_ERR_NONE) {
…
}
…
OSMemPut(&MyPartition,block,&err);
…
}
/* allocate */
/* deallocate */
Example
•
•
•
•
Memory block is not
typed: reader and write
“agrees” on the content’s
format
Once message is written
and posted in the queue,
originator must not touch
it
Once message received
and processed, memory
block is put back in the
partition
To prevent problems if
partition runs out of
available blocks, a
semaphore can be used
to control access to it