[GitHub] [qpid-dispatch] franz1981 commented on a change in pull request #525: DISPATCH-1372 alloc_pool intrusive linked list can be replaced by a linked stack

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franz1981 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_r296309434
 
 

 ##########
 File path: src/alloc_pool.c
 ##########
 @@ -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:
   We can try to reorder fields and see if it will get better cache localty: I see that `qd_alloc_linked_stack_t` is suboptimal, but I've just tried to put `base_chunk` near to the most accessed fields to make used of the adiacent line prefetching of many Intel CPUs; so I've focused just on that...
   I can see too that `CAPACITY` could be changed to improve things too...

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