#define ALLOC_MINBITS		3	/* smallest chunk size is 8 bytes */
#define ALLOCSET_NUM_FREELISTS	11
#define ALLOC_CHUNK_LIMIT	(1 << (ALLOCSET_NUM_FREELISTS-1+ALLOC_MINBITS))
#define ALLOC_CHUNK_FRACTION	4  /* Size of largest chunk that we use a fixed size for */

typedef struct AllocSetContext
{
	MemoryContextData header;	/* Standard memory-context fields */
	/* Info about storage allocated in this context: */
	AllocBlock	blocks;			/* head of list of blocks in this set */
	AllocChunk	freelist[ALLOCSET_NUM_FREELISTS];	/* free chunk lists */
	/* Allocation parameters for this context: */
	Size		initBlockSize;	/* initial block size */
	Size		maxBlockSize;	/* maximum block size */
	Size		nextBlockSize;	/* next block size to allocate */
	Size		allocChunkLimit;	/* effective chunk size limit */
	AllocBlock	keeper;			/* keep this block over resets */
	/* freelist this context could be put in, or -1 if not a candidate: */
	int			freeListIndex;	/* index in context_freelists[], or -1 */
} AllocSetContext;

typedef AllocSetContext *AllocSet;