Allocation

There are several primitive operations for the allocation. Some of them are shown in the Figure 3.13.

  

Figure 3.13: Primitive Operations of Allocation

The findChunk()

private operation picks up an appropriate free Chunk from the freeList by tracing the list.

The split()

private operation (See Figure 3.13) splits the free Chunk picked up by the findChunk and generates a newly allocated Chunk. If the split free Chunk were smaller than the minimum size of chunks in the Arena, the operation would not actually split the free Chunk and allocate the whole Chunk instead.

The splitTopChunk()

private operation is similar to the split operation. The difference is that this primitive operation is invoked when there are no appropriate free Chunks in the freeList, and it splits the topChunk instead.

The destroyChunk()

private operation destroys an allocated Chunk and restores it to the freeList. There are four types of destruction operations depending on the usage of the immediate Chunks. If the immediate Chunks are not in use, the Chunk is just inserted into the freeList. If any of the immediate Chunks are free, this operation consolidates them into a single Chunk (See Figure 3.13).

The consolidateIntoTopChunk()

private operation is invoked after the destroyChunk operation. If the previous Chunk of the topChunk has just been freed by the destroyChunk operation, this primitive operation consolidates the Chunk with the topChunk.

The allocate()

protected operation invokes the findChunk, split, and splitTopChunk operations to generate a new Chunk.

The destroy()

protected operation invokes the destroyChunk operation and the ConsolidateIntoTopChunk operation to restore an allocated Chunk to the free Chunks.