From: Willy Tarreau <w@1wt.eu>
Date: Tue, 15 Nov 2022 07:08:24 +0000 (+0100)
Subject: OPTIM: ebtree: make ebmb_insert_prefix() keep a copy the new node's pfx
X-Git-Tag: v2.7-dev9~65
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bf13e53964228eece9d5d532943720bd9af7915b;p=thirdparty%2Fhaproxy.git

OPTIM: ebtree: make ebmb_insert_prefix() keep a copy the new node's pfx

looking at a perf profile while loading a conf with a huge map, it
appeared that there was a hot spot on the access to the new node's
prefix, which is unexpectedly being reloaded for each visited node
during the tree descent. Better keep a copy of it because with large
trees that don't fit into the L3 cache the memory bandwidth is scarce.
Doing so reduces the load time from 8.0 to 7.5 seconds.
---

diff --git a/include/import/ebmbtree.h b/include/import/ebmbtree.h
index b2dd1447a8..fc6a5002ee 100644
--- a/include/import/ebmbtree.h
+++ b/include/import/ebmbtree.h
@@ -618,6 +618,8 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 	eb_troot_t *new_left, *new_rght;
 	eb_troot_t *new_leaf;
 	int old_node_bit;
+	unsigned int npfx = new->node.pfx;
+	unsigned int npfx1 = npfx << 1;
 
 	side = EB_LEFT;
 	troot = root->b[EB_LEFT];
@@ -631,8 +633,8 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 	}
 
 	len <<= 3;
-	if (len > new->node.pfx)
-		len = new->node.pfx;
+	if (len > npfx)
+		len = npfx;
 
 	/* The tree descent is fairly easy :
 	 *  - first, check if we have reached a leaf node
@@ -690,11 +692,11 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 		 * we visit, otherwise we have to stop going down. The following
 		 * test is able to stop before both normal and cover nodes.
 		 */
-		if (bit >= (new->node.pfx << 1) && (new->node.pfx << 1) < old_node_bit) {
+		if (bit >= npfx1 && npfx1 < old_node_bit) {
 			/* insert cover node here on the left */
 			new->node.node_p = old->node.node_p;
 			up_ptr = &old->node.node_p;
-			new->node.bit = new->node.pfx << 1;
+			new->node.bit = npfx1;
 			diff = -1;
 			goto insert_above;
 		}
@@ -718,7 +720,7 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 			 * the left. For that, we go down on the left and the leaf detection
 			 * code will finish the job.
 			 */
-			if ((new->node.pfx << 1) == old_node_bit) {
+			if (npfx1 == old_node_bit) {
 				root = &old->node.branches;
 				side = EB_LEFT;
 				troot = root->b[side];
@@ -774,8 +776,8 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 	/* first we want to ensure that we compare the correct bit, which means
 	 * the largest common to both nodes.
 	 */
-	if (bit > new->node.pfx)
-		bit = new->node.pfx;
+	if (bit > npfx)
+		bit = npfx;
 	if (bit > old->node.pfx)
 		bit = old->node.pfx;
 
@@ -786,7 +788,7 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 	 * node insertion.
 	 */
 	diff = 0;
-	if (bit < old->node.pfx && bit < new->node.pfx)
+	if (bit < old->node.pfx && bit < npfx)
 		diff = cmp_bits(new->key, old->key, bit);
 
 	if (diff == 0) {
@@ -796,7 +798,7 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 		 * on the right.
 		 */
 		new->node.bit--; /* anticipate cover node insertion */
-		if (new->node.pfx == old->node.pfx) {
+		if (npfx == old->node.pfx) {
 			new->node.bit = -1; /* mark as new dup tree, just in case */
 
 			if (unlikely(eb_gettag(root_right))) {
@@ -815,7 +817,7 @@ __ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int l
 			/* otherwise fall through to insert first duplicate */
 		}
 		/* otherwise we just rely on the tests below to select the right side */
-		else if (new->node.pfx < old->node.pfx)
+		else if (npfx < old->node.pfx)
 			diff = -1; /* force insertion to left side */
 	}