astitcher commented on a change in pull request #525: DISPATCH-1372 alloc_pool
intrusive linked list can be replaced by a linked stack
URL: https://github.com/apache/qpid-dispatch/pull/525#discussion_r297216711
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File path: src/alloc_pool.c
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@@ -44,20 +46,97 @@ DEQ_DECLARE(qd_alloc_type_t, qd_alloc_type_list_t);
#define PATTERN_BACK 0xbabecafe
struct qd_alloc_item_t {
- DEQ_LINKS(qd_alloc_item_t);
uint32_t sequence;
#ifdef QD_MEMORY_DEBUG
qd_alloc_type_desc_t *desc;
uint32_t header;
#endif
};
-DEQ_DECLARE(qd_alloc_item_t, qd_alloc_item_list_t);
+#define CHUNK_SIZE 128/sizeof(void*)
+struct qd_alloc_chunk_t {
+ qd_alloc_chunk_t *prev;
+ qd_alloc_item_t *items[CHUNK_SIZE];
+ qd_alloc_chunk_t *next;
+};
+
+struct qd_alloc_linked_stack_t {
+ //the base
+ qd_alloc_chunk_t *top_chunk;
+ uint32_t top; //qd_alloc_item* top_item =
top_chunk->items[top+1] <-> top > 0
Review comment:
On a 64 bit machine you'll get padding after the uint32 (`top`) to pad it
out to 64 bits. Everything else in the struct is 64 bits (pointers) so to avoid
the padding in the middle of the struct you want to put `top` at the end of the
struct.
[On a 32 bit machine this is not a concern, but don't care as much about
them anyway].
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