The patch titled
Subject: rbtree: optimize case selection logic in __rb_erase_color()
has been added to the -mm tree. Its filename is
rbtree-optimize-case-selection-logic-in-__rb_erase_color.patch
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From: Michel Lespinasse <walken@xxxxxxxxxx>
Subject: rbtree: optimize case selection logic in __rb_erase_color()
In __rb_erase_color(), we have to select one of 3 cases depending on the
color on the 'other' node children. If both children are black, we flip a
few node colors and iterate. Otherwise, we do either one or two tree
rotations, depending on the color of the 'other' child opposite to 'node',
and then we are done.
The corresponding logic had duplicate checks for the color of the 'other'
child opposite to 'node'. It was checking it first to determine if both
children are black, and then to determine how many tree rotations are
required. Rearrange the logic to avoid that extra check.
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Daniel Santos <daniel.santos@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/rbtree.c | 68 +++++++++++++++++++++----------------------------
1 file changed, 30 insertions(+), 38 deletions(-)
diff -puN lib/rbtree.c~rbtree-optimize-case-selection-logic-in-__rb_erase_color lib/rbtree.c
--- a/lib/rbtree.c~rbtree-optimize-case-selection-logic-in-__rb_erase_color
+++ a/lib/rbtree.c
@@ -283,28 +283,24 @@ static void __rb_erase_color(struct rb_n
__rb_rotate_left(parent, root);
other = parent->rb_right;
}
- if ((!other->rb_left || rb_is_black(other->rb_left)) &&
- (!other->rb_right || rb_is_black(other->rb_right)))
- {
- rb_set_red(other);
- node = parent;
- parent = rb_parent(node);
- }
- else
- {
- if (!other->rb_right || rb_is_black(other->rb_right))
- {
- rb_set_black(other->rb_left);
+ if (!other->rb_right || rb_is_black(other->rb_right)) {
+ if (!other->rb_left ||
+ rb_is_black(other->rb_left)) {
rb_set_red(other);
- __rb_rotate_right(other, root);
- other = parent->rb_right;
+ node = parent;
+ parent = rb_parent(node);
+ continue;
}
- rb_set_color(other, rb_color(parent));
- rb_set_black(parent);
- rb_set_black(other->rb_right);
- __rb_rotate_left(parent, root);
- break;
+ rb_set_black(other->rb_left);
+ rb_set_red(other);
+ __rb_rotate_right(other, root);
+ other = parent->rb_right;
}
+ rb_set_color(other, rb_color(parent));
+ rb_set_black(parent);
+ rb_set_black(other->rb_right);
+ __rb_rotate_left(parent, root);
+ break;
} else {
other = parent->rb_left;
if (rb_is_red(other))
@@ -314,28 +310,24 @@ static void __rb_erase_color(struct rb_n
__rb_rotate_right(parent, root);
other = parent->rb_left;
}
- if ((!other->rb_left || rb_is_black(other->rb_left)) &&
- (!other->rb_right || rb_is_black(other->rb_right)))
- {
- rb_set_red(other);
- node = parent;
- parent = rb_parent(node);
- }
- else
- {
- if (!other->rb_left || rb_is_black(other->rb_left))
- {
- rb_set_black(other->rb_right);
+ if (!other->rb_left || rb_is_black(other->rb_left)) {
+ if (!other->rb_right ||
+ rb_is_black(other->rb_right)) {
rb_set_red(other);
- __rb_rotate_left(other, root);
- other = parent->rb_left;
+ node = parent;
+ parent = rb_parent(node);
+ continue;
}
- rb_set_color(other, rb_color(parent));
- rb_set_black(parent);
- rb_set_black(other->rb_left);
- __rb_rotate_right(parent, root);
- break;
+ rb_set_black(other->rb_right);
+ rb_set_red(other);
+ __rb_rotate_left(other, root);
+ other = parent->rb_left;
}
+ rb_set_color(other, rb_color(parent));
+ rb_set_black(parent);
+ rb_set_black(other->rb_left);
+ __rb_rotate_right(parent, root);
+ break;
}
}
}
_
Subject: Subject: rbtree: optimize case selection logic in __rb_erase_color()
Patches currently in -mm which might be from walken@xxxxxxxxxx are
slab-do-not-call-compound_head-in-page_get_cache.patch
rbtree-reference-documentation-rbtreetxt-for-usage-instructions.patch
rbtree-empty-nodes-have-no-color.patch
rbtree-fix-incorrect-rbtree-node-insertion-in-fs-proc-proc_sysctlc.patch
rbtree-move-some-implementation-details-from-rbtreeh-to-rbtreec.patch
rbtree-performance-and-correctness-test.patch
rbtree-break-out-of-rb_insert_color-loop-after-tree-rotation.patch
rbtree-adjust-root-color-in-rb_insert_color-only-when-necessary.patch
rbtree-low-level-optimizations-in-rb_insert_color.patch
rbtree-adjust-node-color-in-__rb_erase_color-only-when-necessary.patch
rbtree-optimize-case-selection-logic-in-__rb_erase_color.patch
rbtree-low-level-optimizations-in-__rb_erase_color.patch
rbtree-coding-style-adjustments.patch
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