ganeshmurthy 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_r298281051
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File path: src/alloc_pool.c
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@@ -44,20 +46,142 @@ 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);
+//128 has been chosen because many CPUs arch use an
+//adiacent line prefetching optimization that load
+//2*cache line bytes in batch
+#define CHUNK_SIZE 128/sizeof(void*)
+struct qd_alloc_chunk_t {
Review comment:
So assuming sizeof(void*) in a 64 bit machine is 8, 128/8 = 16
qd_alloc_chunk_t will have
1. 8 bytes for prev
2. 16 items (qd_alloc_item_ts)
3. 8 bytes for next
======================
Total = 128 + 16 = 144 bytes.
=======================
But Adjacent Cache-Line Prefetch size ie 128 bytes. Looks like 144 bytes
will not fit into one Adjacent Cache-Line Prefetch. So, does it make sense to
move "items" as the first member of qd_alloc_chunk_t in which case we could use
the DEQ for prev and next
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