From: Arran Cudbard-Bell <a.cudbardb@freeradius.org>
Date: Tue, 17 Aug 2021 17:50:17 +0000 (-0500)
Subject: Pre-allocate LST stack memory
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=478a84ce5c281d70545d826d9bc9b7f663842817;p=thirdparty%2Ffreeradius-server.git

Pre-allocate LST stack memory

This is mostly to ensure good locality
---

diff --git a/src/lib/util/lst.c b/src/lib/util/lst.c
index c44d7fd5c01..4c39734e5fd 100644
--- a/src/lib/util/lst.c
+++ b/src/lib/util/lst.c
@@ -144,7 +144,7 @@ bool is_bucket(fr_lst_t *lst, stack_index_t idx)
  * 2. one can fetch and modify arbitrary stack items; when array elements must be
  *    moved to keep them contiguous, the pivot stack entries must change to match.
  */
-static pivot_stack_t *stack_alloc(TALLOC_CTX *ctx)
+static inline CC_HINT(always_inline, nonnull) pivot_stack_t *stack_alloc(TALLOC_CTX *ctx)
 {
 	pivot_stack_t	*s;
 
@@ -230,8 +230,18 @@ fr_lst_t *_fr_lst_alloc(TALLOC_CTX *ctx, fr_lst_cmp_t cmp, char const *type, siz
 {
 	fr_lst_t	*lst;
 
-	lst = talloc_zero(ctx, fr_lst_t);
-	if (!lst) return NULL;
+	/*
+	 *	Pre-allocate stack memory as it is
+	 *	unlikely to need to grow in practice.
+	 *
+	 *	We don't pre-allocate the array of elements
+	 *	If we pre-allocated the array of elements
+	 *	we'd end up wasting that memory as soon as
+	 *	we needed to expand the array.
+	 */
+	lst = talloc_zero_pooled_object(ctx, fr_lst_t, 2,
+					sizeof(pivot_stack_t) + (INITIAL_STACK_CAPACITY * sizeof(fr_lst_index_t)));
+	if (unlikely(!lst)) return NULL;
 
 	lst->capacity = INITIAL_CAPACITY;
 	lst->p = talloc_array(lst, void *, lst->capacity);