CMMemoryPool
An object that optimizes memory allocation when working with large blocks of memory.
Overview
An instance of CMMemoryPool is a memory allocation service that holds a pool of recently deallocated memory. Its purpose is to speed up subsequent allocations of the same size. Use this API in cases where you need to repeatedly allocate large blocks of memory, such as a video encoding app that outputs compressed data.
This object allocates memory by page. It doesn’t suballocate memory within pages, so don’t use it to allocate small blocks. For example, when calling the CMBlockBufferCreateWithMemoryBlock(allocator:memoryBlock:blockLength:blockAllocator:customBlockSource:offsetToData:dataLength:flags:blockBufferOut:) function, you can use it as the blockAllocator argument, but not as the structureAllocator argument (use kCFAllocatorDefault instead).
When you no longer need to allocate memory from the pool, invalidate it by calling the CMMemoryPoolInvalidate(_:) function, which tells the pool to stop holding memory for reuse.
A memory pool deallocates memory if it isn’t reused in 0.5 seconds, so that short-term peak usage doesn’t cause persistent bloat. You can override this period by specifying a value for kCMMemoryPoolOption_AgeOutPeriod. The system does this “aging out” during the pool’s CFAllocatorAllocate(_:_:_:) and CFAllocatorDeallocate(_:_:) calls.