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Date: Thu, 27 Jun 2019 21:50:08 -0700
From: Michel Lespinasse <walken@...gle.com>
To: Davidlohr Bueso <dave@...olabs.net>,
Peter Zijlstra <peterz@...radead.org>,
David Howells <dhowells@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Michel Lespinasse <walken@...gle.com>
Subject: [PATCH] rbtree: avoid generating code twice for the cached versions
As was already noted in rbtree.h, the logic to cache rb_first (or rb_last)
can easily be implemented externally to the core rbtree api.
Change the implementation to do just that. Previously the update of
rb_leftmost was wired deeper into the implemntation, but there were
some disadvantages to that - mostly, lib/rbtree.c had separate
instantiations for rb_insert_color() vs rb_insert_color_cached(), as well
as rb_erase() vs rb_erase_cached(), which were doing exactly the same
thing save for the rb_leftmost update at the start of either function.
Change-Id: I0cb62be774fc0138b81188e6ae81d5f1da64578d
Signed-off-by: Michel Lespinasse <walken@...gle.com>
---
include/linux/rbtree.h | 70 +++++++++++++++++++++-----------
include/linux/rbtree_augmented.h | 27 +++++-------
lib/rbtree.c | 40 ++----------------
3 files changed, 59 insertions(+), 78 deletions(-)
diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index fcbeed4053ef..9e8d41a90072 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -44,25 +44,9 @@ struct rb_root {
struct rb_node *rb_node;
};
-/*
- * Leftmost-cached rbtrees.
- *
- * We do not cache the rightmost node based on footprint
- * size vs number of potential users that could benefit
- * from O(1) rb_last(). Just not worth it, users that want
- * this feature can always implement the logic explicitly.
- * Furthermore, users that want to cache both pointers may
- * find it a bit asymmetric, but that's ok.
- */
-struct rb_root_cached {
- struct rb_root rb_root;
- struct rb_node *rb_leftmost;
-};
-
#define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))
#define RB_ROOT (struct rb_root) { NULL, }
-#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
#define rb_entry(ptr, type, member) container_of(ptr, type, member)
#define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL)
@@ -84,12 +68,6 @@ extern struct rb_node *rb_prev(const struct rb_node *);
extern struct rb_node *rb_first(const struct rb_root *);
extern struct rb_node *rb_last(const struct rb_root *);
-extern void rb_insert_color_cached(struct rb_node *,
- struct rb_root_cached *, bool);
-extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
-/* Same as rb_first(), but O(1) */
-#define rb_first_cached(root) (root)->rb_leftmost
-
/* Postorder iteration - always visit the parent after its children */
extern struct rb_node *rb_first_postorder(const struct rb_root *);
extern struct rb_node *rb_next_postorder(const struct rb_node *);
@@ -99,8 +77,6 @@ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);
extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);
-extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
- struct rb_root_cached *root);
static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
struct rb_node **rb_link)
@@ -148,4 +124,50 @@ static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent
typeof(*pos), field); 1; }); \
pos = n)
+/*
+ * Leftmost-cached rbtrees.
+ *
+ * We do not cache the rightmost node based on footprint
+ * size vs number of potential users that could benefit
+ * from O(1) rb_last(). Just not worth it, users that want
+ * this feature can always implement the logic explicitly.
+ * Furthermore, users that want to cache both pointers may
+ * find it a bit asymmetric, but that's ok.
+ */
+struct rb_root_cached {
+ struct rb_root rb_root;
+ struct rb_node *rb_leftmost;
+};
+
+#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
+
+/* Same as rb_first(), but O(1) */
+#define rb_first_cached(root) (root)->rb_leftmost
+
+static inline void rb_insert_color_cached(struct rb_node *node,
+ struct rb_root_cached *root,
+ bool leftmost)
+{
+ if (leftmost)
+ root->rb_leftmost = node;
+ rb_insert_color(node, &root->rb_root);
+}
+
+static inline void rb_erase_cached(struct rb_node *node,
+ struct rb_root_cached *root)
+{
+ if (root->rb_leftmost == node)
+ root->rb_leftmost = rb_next(node);
+ rb_erase(node, &root->rb_root);
+}
+
+static inline void rb_replace_node_cached(struct rb_node *victim,
+ struct rb_node *new,
+ struct rb_root_cached *root)
+{
+ if (root->rb_leftmost == victim)
+ root->rb_leftmost = new;
+ rb_replace_node(victim, new, &root->rb_root);
+}
+
#endif /* _LINUX_RBTREE_H */
diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index 9510c677ac70..f1ed3fc80bbb 100644
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -42,10 +42,9 @@ struct rb_augment_callbacks {
void (*rotate)(struct rb_node *old, struct rb_node *new);
};
-extern void __rb_insert_augmented(struct rb_node *node,
- struct rb_root *root,
- bool newleft, struct rb_node **leftmost,
+extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
+
/*
* Fixup the rbtree and update the augmented information when rebalancing.
*
@@ -60,7 +59,7 @@ static inline void
rb_insert_augmented(struct rb_node *node, struct rb_root *root,
const struct rb_augment_callbacks *augment)
{
- __rb_insert_augmented(node, root, false, NULL, augment->rotate);
+ __rb_insert_augmented(node, root, augment->rotate);
}
static inline void
@@ -68,8 +67,9 @@ rb_insert_augmented_cached(struct rb_node *node,
struct rb_root_cached *root, bool newleft,
const struct rb_augment_callbacks *augment)
{
- __rb_insert_augmented(node, &root->rb_root,
- newleft, &root->rb_leftmost, augment->rotate);
+ if (newleft)
+ root->rb_leftmost = node;
+ rb_insert_augmented(node, &root->rb_root, augment);
}
#define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield, \
@@ -162,7 +162,6 @@ extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
static __always_inline struct rb_node *
__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
- struct rb_node **leftmost,
const struct rb_augment_callbacks *augment)
{
struct rb_node *child = node->rb_right;
@@ -170,9 +169,6 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
struct rb_node *parent, *rebalance;
unsigned long pc;
- if (leftmost && node == *leftmost)
- *leftmost = rb_next(node);
-
if (!tmp) {
/*
* Case 1: node to erase has no more than 1 child (easy!)
@@ -272,8 +268,7 @@ static __always_inline void
rb_erase_augmented(struct rb_node *node, struct rb_root *root,
const struct rb_augment_callbacks *augment)
{
- struct rb_node *rebalance = __rb_erase_augmented(node, root,
- NULL, augment);
+ struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
if (rebalance)
__rb_erase_color(rebalance, root, augment->rotate);
}
@@ -282,11 +277,9 @@ static __always_inline void
rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
const struct rb_augment_callbacks *augment)
{
- struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
- &root->rb_leftmost,
- augment);
- if (rebalance)
- __rb_erase_color(rebalance, &root->rb_root, augment->rotate);
+ if (root->rb_leftmost == node)
+ root->rb_leftmost = rb_next(node);
+ rb_erase_augmented(node, &root->rb_root, augment);
}
#endif /* _LINUX_RBTREE_AUGMENTED_H */
diff --git a/lib/rbtree.c b/lib/rbtree.c
index d3ff682fd4b8..432e9c540178 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -95,14 +95,10 @@ __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
static __always_inline void
__rb_insert(struct rb_node *node, struct rb_root *root,
- bool newleft, struct rb_node **leftmost,
void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
{
struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;
- if (newleft)
- *leftmost = node;
-
while (true) {
/*
* Loop invariant: node is red.
@@ -449,38 +445,19 @@ static const struct rb_augment_callbacks dummy_callbacks = {
void rb_insert_color(struct rb_node *node, struct rb_root *root)
{
- __rb_insert(node, root, false, NULL, dummy_rotate);
+ __rb_insert(node, root, dummy_rotate);
}
EXPORT_SYMBOL(rb_insert_color);
void rb_erase(struct rb_node *node, struct rb_root *root)
{
struct rb_node *rebalance;
- rebalance = __rb_erase_augmented(node, root,
- NULL, &dummy_callbacks);
+ rebalance = __rb_erase_augmented(node, root, &dummy_callbacks);
if (rebalance)
____rb_erase_color(rebalance, root, dummy_rotate);
}
EXPORT_SYMBOL(rb_erase);
-void rb_insert_color_cached(struct rb_node *node,
- struct rb_root_cached *root, bool leftmost)
-{
- __rb_insert(node, &root->rb_root, leftmost,
- &root->rb_leftmost, dummy_rotate);
-}
-EXPORT_SYMBOL(rb_insert_color_cached);
-
-void rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
-{
- struct rb_node *rebalance;
- rebalance = __rb_erase_augmented(node, &root->rb_root,
- &root->rb_leftmost, &dummy_callbacks);
- if (rebalance)
- ____rb_erase_color(rebalance, &root->rb_root, dummy_rotate);
-}
-EXPORT_SYMBOL(rb_erase_cached);
-
/*
* Augmented rbtree manipulation functions.
*
@@ -489,10 +466,9 @@ EXPORT_SYMBOL(rb_erase_cached);
*/
void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
- bool newleft, struct rb_node **leftmost,
void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
{
- __rb_insert(node, root, newleft, leftmost, augment_rotate);
+ __rb_insert(node, root, augment_rotate);
}
EXPORT_SYMBOL(__rb_insert_augmented);
@@ -603,16 +579,6 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new,
}
EXPORT_SYMBOL(rb_replace_node);
-void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
- struct rb_root_cached *root)
-{
- rb_replace_node(victim, new, &root->rb_root);
-
- if (root->rb_leftmost == victim)
- root->rb_leftmost = new;
-}
-EXPORT_SYMBOL(rb_replace_node_cached);
-
void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
struct rb_root *root)
{
--
2.22.0.410.gd8fdbe21b5-goog
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