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
memory alllocations so they can be freed as well.
If the there are existing mp_blocks in the mem_pool's linked list of
mp_blocks, then the mp_block for a large allocation is inserted
after 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
in the search for available space in future requests, as 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@xxxxxxxxxxxxx>
---
mem-pool.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++------------
mem-pool.h | 10 ++++++++++
2 files changed, 61 insertions(+), 12 deletions(-)
diff --git a/mem-pool.c b/mem-pool.c
index a5d5eed923..4e544459e9 100644
--- a/mem-pool.c
+++ b/mem-pool.c
@@ -5,7 +5,14 @@
#include "cache.h"
#include "mem-pool.h"
-static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc)
+#define BLOCK_GROWTH_SIZE 1024*1024 - sizeof(struct mp_block);
+
+/*
+ * Allocate a new mp_block and insert it after the block specified in
+ * `insert_after`. If `insert_after` is NULL, then insert block at the
+ * head of the linked list.
+ */
+static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc, struct mp_block *insert_after)
{
struct mp_block *p;
size_t total_alloc = st_add(offsetof(struct mp_block, space), block_alloc);
@@ -13,14 +20,51 @@ static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t b
mem_pool->pool_alloc = st_add(mem_pool->pool_alloc, total_alloc);
p = xmalloc(total_alloc);
- p->next_block = mem_pool->mp_block;
p->next_free = (char *)p->space;
p->end = p->next_free + block_alloc;
- mem_pool->mp_block = p;
+
+ if (insert_after) {
+ p->next_block = insert_after->next_block;
+ insert_after->next_block = p;
+ } else {
+ p->next_block = mem_pool->mp_block;
+ mem_pool->mp_block = p;
+ }
return p;
}
+void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size)
+{
+ struct mem_pool *pool;
+
+ if (*mem_pool)
+ return;
+
+ pool = xcalloc(1, sizeof(*pool));
+
+ pool->block_alloc = BLOCK_GROWTH_SIZE;
+
+ if (initial_size > 0)
+ mem_pool_alloc_block(pool, initial_size, NULL);
+
+ *mem_pool = pool;
+}
+
+void mem_pool_discard(struct mem_pool *mem_pool)
+{
+ struct mp_block *block, *block_to_free;
+
+ while ((block = mem_pool->mp_block))
+ {
+ block_to_free = block;
+ block = block->next_block;
+ free(block_to_free);
+ }
+
+ free(mem_pool);
+}
+
void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
{
struct mp_block *p = NULL;
@@ -33,15 +77,10 @@ void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
if (mem_pool->mp_block &&
mem_pool->mp_block->end - mem_pool->mp_block->next_free >= len)
p = mem_pool->mp_block;
-
- if (!p) {
- if (len >= (mem_pool->block_alloc / 2)) {
- mem_pool->pool_alloc += len;
- return xmalloc(len);
- }
-
- p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc);
- }
+ else if (len >= (mem_pool->block_alloc / 2))
+ p = mem_pool_alloc_block(mem_pool, len, mem_pool->mp_block);
+ else
+ p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc, NULL);
r = p->next_free;
p->next_free += len;
diff --git a/mem-pool.h b/mem-pool.h
index 829ad58ecf..f75b3365d5 100644
--- a/mem-pool.h
+++ b/mem-pool.h
@@ -21,6 +21,16 @@ struct mem_pool {
size_t pool_alloc;
};
+/*
+ * 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.
*/
--
2.14.3
