The patch titled
Subject: lib/rbtree: use '+' instead of '|' for setting color.
has been added to the -mm mm-nonmm-unstable branch. Its filename is
lib-rbtree-use-instead-of-for-setting-color.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-rbtree-use-instead-of-for-setting-color.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Noah Goldstein <goldstein.w.n@xxxxxxxxx>
Subject: lib/rbtree: use '+' instead of '|' for setting color.
Date: Tue, 4 Apr 2023 17:13:51 -0500
This has a slight benefit for x86 and has no effect on other targets.
The benefit to x86 is it change the codegen for setting a node to block
from `mov %r0, %r1; or $RB_BLACK, %r1` to `lea RB_BLACK(%r0), %r1` which
saves an instructions.
In all other cases it just replace ALU with ALU (or -> and) which
perform the same on all machines I am aware of.
Total instructions in rbtree.o:
Before - 802
After - 782
so it saves about 20 `mov` instructions.
Link: https://lkml.kernel.org/r/20230404221350.3806566-1-goldstein.w.n@xxxxxxxxx
Signed-off-by: Noah Goldstein <goldstein.w.n@xxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rbtree_augmented.h | 4 ++--
lib/rbtree.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
--- a/include/linux/rbtree_augmented.h~lib-rbtree-use-instead-of-for-setting-color
+++ a/include/linux/rbtree_augmented.h
@@ -156,13 +156,13 @@ RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,
static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
- rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
+ rb->__rb_parent_color = rb_color(rb) + (unsigned long)p;
}
static inline void rb_set_parent_color(struct rb_node *rb,
struct rb_node *p, int color)
{
- rb->__rb_parent_color = (unsigned long)p | color;
+ rb->__rb_parent_color = (unsigned long)p + color;
}
static inline void
--- a/lib/rbtree.c~lib-rbtree-use-instead-of-for-setting-color
+++ a/lib/rbtree.c
@@ -58,7 +58,7 @@
static inline void rb_set_black(struct rb_node *rb)
{
- rb->__rb_parent_color |= RB_BLACK;
+ rb->__rb_parent_color += RB_BLACK;
}
static inline struct rb_node *rb_red_parent(struct rb_node *red)
_
Patches currently in -mm which might be from goldstein.w.n@xxxxxxxxx are
lib-rbtree-use-instead-of-for-setting-color.patch
