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rbtree: inline rb_first()

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Patch series "rbree: inline rb_first() and rb_last()".

Inline these two small helpers, heavily used in TCP and FQ packet scheduler,
and in many other places.

This reduces kernel text size, and brings an 1.5 % improvement on network
TCP stress test.


This patch (of 2):

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

It also reduces vmlinux text size by 744 bytes on a typical x86_64 build.

Before:

size vmlinux
   text	   data	    bss	    dec	    hex	filename
34812525	22177365	5685248	62675138	3bc58c2	vmlinux

After:

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

[ojeda@kernel.org: fix rust build]
  Link: https://lkml.kernel.org/r/20251120085518.1463498-1-ojeda@kernel.org
Link: https://lkml.kernel.org/r/20251114140646.3817319-1-edumazet@google.com
Link: https://lkml.kernel.org/r/20251114140646.3817319-2-edumazet@google.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Stehen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Eric Dumazet
2025-11-14 14:06:45 +00:00
committed by Andrew Morton
parent bc947af677
commit c2d2dad245
3 changed files with 20 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
include/linux/rbtree.h
View File

@@ -43,7 +43,21 @@ extern void rb_erase(struct rb_node *, struct rb_root *);
/* Find logical next and previous nodes in a tree */
extern struct rb_node *rb_next(const struct rb_node *);
extern struct rb_node *rb_prev(const struct rb_node *);
extern struct rb_node *rb_first(const struct rb_root *);
/*
* This function returns the first node (in sort order) of the tree.
*/
static inline struct rb_node *rb_first(const struct rb_root *root)
{
struct rb_node *n;
n = root->rb_node;
if (!n)
return NULL;
while (n->rb_left)
n = n->rb_left;
return n;
}
extern struct rb_node *rb_last(const struct rb_root *);
/* Postorder iteration - always visit the parent after its children */

16
lib/rbtree.c
View File

@@ -460,22 +460,6 @@ void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
}
EXPORT_SYMBOL(__rb_insert_augmented);
/*
* This function returns the first node (in sort order) of the tree.
*/
struct rb_node *rb_first(const struct rb_root *root)
{
struct rb_node *n;
n = root->rb_node;
if (!n)
return NULL;
while (n->rb_left)
n = n->rb_left;
return n;
}
EXPORT_SYMBOL(rb_first);
struct rb_node *rb_last(const struct rb_root *root)
{
struct rb_node *n;

5
rust/helpers/rbtree.c
View File

@@ -7,3 +7,8 @@ void rust_helper_rb_link_node(struct rb_node *node, struct rb_node *parent,
{
rb_link_node(node, parent, rb_link);
}
struct rb_node *rust_helper_rb_first(const struct rb_root *root)
{
return rb_first(root);
}