mem-pool: add life cycle management functions

Add initialization and discard functions to mem_pool type. As the
memory allocated by mem_pool can now be freed, we also track the large
allocations.

If the there are existing mp_blocks in the mem_poo's linked list of
mp_blocksl, then the mp_block for a large allocation is inserted
behind the head block. This is because only the head mp_block is considered
when searching for availble space. This results in the following
desirable properties:

1) The mp_block allocated for the large request will not be included
not included in the search for available in future requests, the large
mp_block is sized for the specific request and does not contain any
spare space.

2) The head mp_block will not bumped from considation for future
memory requests just because a request for a large chunk of memory
came in.

These changes are in preparation for a future commit that will utilize
creating and discarding memory pool.

Signed-off-by: Jameson Miller <jamill@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/mem-pool.h b/mem-pool.h
index 829ad58ecf..f75b3365d5 100644
--- a/mem-pool.h
+++ b/mem-pool.h
@@ -22,6 +22,16 @@ struct mem_pool {
 };
 
 /*
+ * Initialize mem_pool with specified initial size.
+ */
+void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size);
+
+/*
+ * Discard a memory pool and free all the memory it is responsible for.
+ */
+void mem_pool_discard(struct mem_pool *mem_pool);
+
+/*
  * Alloc memory from the mem_pool.
  */
 void *mem_pool_alloc(struct mem_pool *pool, size_t len);