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rbtree: inline rb_last()

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This is a very small function, inlining it saves 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

[ojeda@kernel.org: fix rust build]
  Link: https://lkml.kernel.org/r/20251120085518.1463498-1-ojeda@kernel.org
Link: https://lkml.kernel.org/r/20251114140646.3817319-3-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 14:06:46 +00:00
committed by Andrew Morton
parent c2d2dad245
commit 94984bfed5
3 changed files with 20 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
include/linux/rbtree.h
View File

@@ -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 *);

13
lib/rbtree.c
View File

@@ -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;

5
rust/helpers/rbtree.c
View File

@@ -12,3 +12,8 @@ struct rb_node *rust_helper_rb_first(const struct rb_root *root)
{
return rb_first(root);
}
struct rb_node *rust_helper_rb_last(const struct rb_root *root)
{
return rb_last(root);
}