[Feature] Smart destructor preallocation based on pool type and statistics

Implement intelligent preallocation strategy for destructor heap:

Long-lived pools (LONG_LIVED flag):
- Fixed preallocation: 32 destructor slots
- No statistical tracking needed (pool lives entire process lifetime)
- Covers typical module/configuration destructor counts

Short-lived pools (default):
- Statistics-based preallocation using entry point data
- Track maximum destructors seen per entry point
- Cap at 64 slots to prevent excessive preallocation
- Simplified max-tracking logic (replaces exponential growth)

Benefits:
- Long-lived: predictable memory usage, no reallocation overhead
- Short-lived: adaptive to actual usage patterns
- Reduced heap resizing operations during destructor addition
- Memory bounded (32 for long-lived, max 64 for short-lived)

Statistics updated on pool deletion to inform future allocations
from same entry point.

diff --git a/src/libutil/mem_pool.c b/src/libutil/mem_pool.c
index b7441ee4bc988bc90d90bf4398d52e6f1600859e..726d66d7d91e213b294b708d908e65fb4b879eab 100644 (file)
--- a/src/libutil/mem_pool.c
+++ b/src/libutil/mem_pool.c
@@ -674,10 +674,20 @@ void rspamd_mempool_add_destructor_full(rspamd_mempool_t *pool,
        if (pool->priv->dtors_heap.a == NULL) {
                rspamd_heap_init(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap);
 
-               /* Reserve space based on statistics */
-               if (pool->priv->entry && pool->priv->entry->cur_dtors > 0) {
+               /* Reserve space based on pool type and statistics */
+               unsigned int preallocate = 0;
+               if (pool->priv->flags & RSPAMD_MEMPOOL_LONG_LIVED) {
+                       /* Long-lived pools: fixed preallocation (32 slots) */
+                       preallocate = 32;
+               }
+               else if (pool->priv->entry && pool->priv->entry->cur_dtors > 0) {
+                       /* Short-lived pools: use statistics, cap at 64 */
+                       preallocate = MIN(pool->priv->entry->cur_dtors, 64);
+               }
+
+               if (preallocate > 0) {
                        kv_resize_safe(struct _pool_destructors, pool->priv->dtors_heap,
-                                                  pool->priv->entry->cur_dtors, cleanup);
+                                                  preallocate, cleanup);
                }
        }
 
@@ -939,27 +949,9 @@ void rspamd_mempool_delete(rspamd_mempool_t *pool)
                if (pool->priv->entry && mempool_entries) {
                        ndtors = rspamd_heap_size(rspamd_mempool_destruct_heap, &pool->priv->dtors_heap);
 
-                       /* Update suggestion using similar logic to variables */
-                       if (pool->priv->entry->cur_dtors < ndtors) {
-                               static const unsigned int max_preallocated_dtors = 128;
-
-                               unsigned int old_guess = pool->priv->entry->cur_dtors;
-                               unsigned int new_guess;
-
-                               if (old_guess == 0) {
-                                       new_guess = MIN(ndtors, max_preallocated_dtors);
-                               }
-                               else {
-                                       if (old_guess * 2 < ndtors) {
-                                               new_guess = MIN(ndtors, max_preallocated_dtors);
-                                       }
-                                       else {
-                                               /* Too large step */
-                                               new_guess = MIN(old_guess * 2, max_preallocated_dtors);
-                                       }
-                               }
-
-                               pool->priv->entry->cur_dtors = new_guess;
+                       /* Track maximum number of destructors seen, cap at 64 */
+                       if (ndtors > pool->priv->entry->cur_dtors) {
+                               pool->priv->entry->cur_dtors = MIN(ndtors, 64);
                        }
                }