linux-kernel - [PATCH 2/2] rbtree: inline rb

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Message-ID: <20251114140646.3817319-3-edumazet@google.com>
Date: Fri, 14 Nov 2025 14:06:46 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, 
	Neal Cardwell <ncardwell@...gle.com>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Eric Dumazet <eric.dumazet@...il.com>, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH 2/2] rbtree: inline rb_last()

This is a very small function, inlining it save cpu cycles in TCP
by reducing register pressure and removing call/ret overhead.

It also reduces vmlinux text size by 122 bytes on a typical x86_64 build.

Before:

size vmlinux
   text    data     bss     dec     hex filename
34811781        22177365        5685248 62674394        3bc55da vmlinux

After:

size vmlinux
   text	   data	    bss	    dec	    hex	filename
34811659	22177365	5685248	62674272	3bc5560	vmlinux

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/rbtree.h | 16 +++++++++++++++-
 lib/rbtree.c           | 13 -------------
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index 484554900f7d3201d41fb29e04fb65fe331eee79..4091e978aef2404b56d7643d9385727c69796678 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -58,7 +58,21 @@ static inline struct rb_node *rb_first(const struct rb_root *root)
 		n = n->rb_left;
 	return n;
 }
-extern struct rb_node *rb_last(const struct rb_root *);
+
+/*
+ * This function returns the last node (in sort order) of the tree.
+ */
+static inline struct rb_node *rb_last(const struct rb_root *root)
+{
+	struct rb_node	*n;
+
+	n = root->rb_node;
+	if (!n)
+		return NULL;
+	while (n->rb_right)
+		n = n->rb_right;
+	return n;
+}
 
 /* Postorder iteration - always visit the parent after its children */
 extern struct rb_node *rb_first_postorder(const struct rb_root *);
diff --git a/lib/rbtree.c b/lib/rbtree.c
index b946eb4b759d3b65f5bc5d54d0377348962bdc56..18d42bcf4ec9d581807179f34561f4561900206d 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -460,19 +460,6 @@ void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
 }
 EXPORT_SYMBOL(__rb_insert_augmented);
 
-struct rb_node *rb_last(const struct rb_root *root)
-{
-	struct rb_node	*n;
-
-	n = root->rb_node;
-	if (!n)
-		return NULL;
-	while (n->rb_right)
-		n = n->rb_right;
-	return n;
-}
-EXPORT_SYMBOL(rb_last);
-
 struct rb_node *rb_next(const struct rb_node *node)
 {
 	struct rb_node *parent;
-- 
2.52.0.rc1.455.g30608eb744-goog