From: Vsevolod Stakhov <vsevolod@rspamd.com>
Date: Tue, 21 Oct 2025 10:34:58 +0000 (+0100)
Subject: [Optimize] Add rspamd_heap_push_slot to eliminate double allocation
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=962c4ef589abce40adaf8835a1b9c89bfc3caa98;p=thirdparty%2Frspamd.git

[Optimize] Add rspamd_heap_push_slot to eliminate double allocation

Add rspamd_heap_push_slot() macro that allocates a slot directly in
the heap and returns a pointer to it, avoiding unnecessary copying.

Previously, memory pool destructors were allocated twice:
1. First allocated in mempool via rspamd_mempool_alloc_
2. Then copied into heap via rspamd_heap_push_safe

New approach:
- rspamd_heap_push_slot allocates zero-initialized slot in heap
- Returns pointer to the slot for direct filling
- User calls rspamd_heap_swim after filling to restore heap property

Benefits:
- Eliminates duplicate allocation of destructor structures
- Reduces memory usage (no temporary allocation in mempool)
- Better cache locality (destructor lives only in heap)
- Same pattern can be used elsewhere for efficient heap usage

Updated rspamd_mempool_add_destructor_full to use new API.
---

diff --git a/src/libutil/heap.h b/src/libutil/heap.h
index 50a2222866..08ed4afab3 100644
--- a/src/libutil/heap.h
+++ b/src/libutil/heap.h
@@ -153,6 +153,22 @@ extern "C" {
 		}                                                            \
 	} while (0)
 
+/**
+ * Allocate slot in heap and return pointer to it (zero-initialized)
+ * User fills the slot, then must call rspamd_heap_swim to restore heap property
+ * Returns NULL on allocation failure
+ */
+#define rspamd_heap_push_slot(name, heap)                                           \
+	({                                                                              \
+		typeof(&kv_A(*(heap), 0)) slot = NULL;                                      \
+		kv_push(typeof(kv_A(*(heap), 0)), *(heap), (typeof(kv_A(*(heap), 0))) {0}); \
+		if (kv_size(*(heap)) > 0) {                                                 \
+			slot = &kv_A(*(heap), kv_size(*(heap)) - 1);                            \
+			slot->idx = kv_size(*(heap)) - 1;                                       \
+		}                                                                           \
+		slot;                                                                       \
+	})
+
 /**
  * Push element to heap (safe version with error handling)
  * Element is copied into the heap array.
diff --git a/src/libutil/mem_pool.c b/src/libutil/mem_pool.c
index d806a34e23..b7441ee4bc 100644
--- a/src/libutil/mem_pool.c
+++ b/src/libutil/mem_pool.c
@@ -670,15 +670,6 @@ void rspamd_mempool_add_destructor_full(rspamd_mempool_t *pool,
 
 	POOL_MTX_LOCK();
 
-	/* Allocate destructor structure */
-	dtor = rspamd_mempool_alloc_(pool, sizeof(*dtor),
-								 RSPAMD_ALIGNOF(struct _pool_destructors), line);
-	dtor->func = func;
-	dtor->data = data;
-	dtor->function = function;
-	dtor->loc = line;
-	dtor->pri = priority;
-
 	/* Initialize heap if not yet created */
 	if (pool->priv->dtors_heap.a == NULL) {
 		rspamd_heap_init(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap);
@@ -690,8 +681,21 @@ void rspamd_mempool_add_destructor_full(rspamd_mempool_t *pool,
 		}
 	}
 
-	/* Push to heap - using non-safe version as we're in mempool */
-	rspamd_heap_push_safe(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap, dtor, cleanup);
+	/* Allocate slot directly in heap (avoids double allocation) */
+	dtor = rspamd_heap_push_slot(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap);
+	if (dtor == NULL) {
+		goto cleanup;
+	}
+
+	/* Fill destructor structure */
+	dtor->func = func;
+	dtor->data = data;
+	dtor->function = function;
+	dtor->loc = line;
+	dtor->pri = priority;
+
+	/* Restore heap property after filling the slot */
+	rspamd_heap_swim(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap, dtor);
 
 	POOL_MTX_UNLOCK();
 	return;