rb_tree: speed-up double rotation
RB_ROTATE_LEFT (and it symmetric twin) modify the rb-tree, adjusting pointers so that what started as a proper tree ends up a proper tree. When two consecutive rotations move the same node up the tree, some of the pointers changed in the first rotation are immediately changed again in the second - namely, the pointer from the rising node to its new parent, and the pointer from that parent back to the rising node. This change removes from RB_ROTATE macros the responsibility for managing those two pointers, and leaves it to the code that calls for rotations to fix up those pointers afterward. That drops a comparison and a pair of assignments from every INSERT_COLOR or REMOVE_COLOR call that ends in a double rotation. A side-effect of this change is that the SWAP_CHILD macro must take as a parameter a pointer to the node that is changing children, where it is now computed from the old child. Since this macro is called in a couple of places besides the RB_ROTATE macros, those calls are also affected. Reviewed by: alc MFC after: 3 weeks Differential Revision: https://reviews.freebsd.org/D36266
This commit is contained in:
parent
f6cc21e8e1
commit
02d0c43c9e
@ -132,7 +132,8 @@ rb_replace_node(struct rb_node *victim, struct rb_node *new,
|
||||
struct rb_root *root)
|
||||
{
|
||||
|
||||
RB_SWAP_CHILD((struct linux_root *)root, victim, new, __entry);
|
||||
RB_SWAP_CHILD((struct linux_root *)root, rb_parent(victim),
|
||||
victim, new, __entry);
|
||||
if (victim->rb_left)
|
||||
RB_SET_PARENT(victim->rb_left, new, __entry);
|
||||
if (victim->rb_right)
|
||||
|
@ -378,31 +378,40 @@ struct { \
|
||||
} while ((rb_update_tmp = RB_PARENT(rb_update_tmp, field)) != NULL); \
|
||||
} while (0)
|
||||
|
||||
#define RB_SWAP_CHILD(head, out, in, field) do { \
|
||||
if (RB_PARENT(out, field) == NULL) \
|
||||
#define RB_SWAP_CHILD(head, par, out, in, field) do { \
|
||||
if (par == NULL) \
|
||||
RB_ROOT(head) = (in); \
|
||||
else if ((out) == RB_LEFT(RB_PARENT(out, field), field)) \
|
||||
RB_LEFT(RB_PARENT(out, field), field) = (in); \
|
||||
else if ((out) == RB_LEFT(par, field)) \
|
||||
RB_LEFT(par, field) = (in); \
|
||||
else \
|
||||
RB_RIGHT(RB_PARENT(out, field), field) = (in); \
|
||||
RB_RIGHT(par, field) = (in); \
|
||||
} while (/*CONSTCOND*/ 0)
|
||||
|
||||
#define RB_ROTATE_LEFT(head, elm, tmp, field) do { \
|
||||
/*
|
||||
* RB_ROTATE macros partially restructure the tree to improve
|
||||
* balance. The ROTATE_RIGHT case is just a reflection of the
|
||||
* ROTATE_LEFT case. Initially, tmp is a right child of elm. After
|
||||
* rotation, elm is a left child of tmp, and the subtree that
|
||||
* represented the items between them, which formerly hung to the left
|
||||
* of tmp now hangs to the right of elm. The parent-child
|
||||
* relationship between elm and its former parent is not changed;
|
||||
* where this macro once updated those fields, that is now left to the
|
||||
* caller of RB_ROTATE to clean up, so that a pair of rotations does
|
||||
* not twice update the came pair of pointer fields with distinct
|
||||
* values.
|
||||
*/
|
||||
#define RB_ROTATE_LEFT(elm, tmp, field) do { \
|
||||
if ((RB_RIGHT(elm, field) = RB_LEFT(tmp, field)) != NULL) { \
|
||||
RB_SET_PARENT(RB_RIGHT(elm, field), elm, field); \
|
||||
} \
|
||||
RB_SET_PARENT(tmp, RB_PARENT(elm, field), field); \
|
||||
RB_SWAP_CHILD(head, elm, tmp, field); \
|
||||
RB_LEFT(tmp, field) = (elm); \
|
||||
RB_SET_PARENT(elm, tmp, field); \
|
||||
} while (/*CONSTCOND*/ 0)
|
||||
|
||||
#define RB_ROTATE_RIGHT(head, elm, tmp, field) do { \
|
||||
#define RB_ROTATE_RIGHT(elm, tmp, field) do { \
|
||||
if ((RB_LEFT(elm, field) = RB_RIGHT(tmp, field)) != NULL) { \
|
||||
RB_SET_PARENT(RB_LEFT(elm, field), elm, field); \
|
||||
} \
|
||||
RB_SET_PARENT(tmp, RB_PARENT(elm, field), field); \
|
||||
RB_SWAP_CHILD(head, elm, tmp, field); \
|
||||
RB_RIGHT(tmp, field) = (elm); \
|
||||
RB_SET_PARENT(elm, tmp, field); \
|
||||
} while (/*CONSTCOND*/ 0)
|
||||
@ -479,8 +488,9 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
|
||||
* when a value has been assigned to 'child' in the previous \
|
||||
* one. \
|
||||
*/ \
|
||||
struct type *child, *parent; \
|
||||
struct type *child, *gpar, *parent; \
|
||||
while ((parent = RB_PARENT(elm, field)) != NULL) { \
|
||||
gpar = RB_PARENT(parent, field); \
|
||||
if (RB_LEFT(parent, field) == elm) { \
|
||||
if (RB_RED_LEFT(parent, field)) { \
|
||||
RB_FLIP_LEFT(parent, field); \
|
||||
@ -496,7 +506,7 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
|
||||
child = elm; \
|
||||
else { \
|
||||
/* coverity[uninit_use] */ \
|
||||
RB_ROTATE_LEFT(head, elm, child, field);\
|
||||
RB_ROTATE_LEFT(elm, child, field); \
|
||||
if (RB_RED_RIGHT(child, field)) \
|
||||
RB_FLIP_LEFT(parent, field); \
|
||||
if (RB_RED_LEFT(child, field)) \
|
||||
@ -507,7 +517,7 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
|
||||
RB_RED_MASK) == 0) \
|
||||
elm = child; \
|
||||
} \
|
||||
RB_ROTATE_RIGHT(head, parent, child, field); \
|
||||
RB_ROTATE_RIGHT(parent, child, field); \
|
||||
} else { \
|
||||
if (RB_RED_RIGHT(parent, field)) { \
|
||||
RB_FLIP_RIGHT(parent, field); \
|
||||
@ -523,7 +533,7 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
|
||||
child = elm; \
|
||||
else { \
|
||||
/* coverity[uninit_use] */ \
|
||||
RB_ROTATE_RIGHT(head, elm, child, field);\
|
||||
RB_ROTATE_RIGHT(elm, child, field); \
|
||||
if (RB_RED_LEFT(child, field)) \
|
||||
RB_FLIP_RIGHT(parent, field); \
|
||||
if (RB_RED_RIGHT(child, field)) \
|
||||
@ -534,8 +544,10 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
|
||||
RB_RED_MASK) == 0) \
|
||||
elm = child; \
|
||||
} \
|
||||
RB_ROTATE_LEFT(head, parent, child, field); \
|
||||
RB_ROTATE_LEFT(parent, child, field); \
|
||||
} \
|
||||
RB_SET_PARENT(child, gpar, field); \
|
||||
RB_SWAP_CHILD(head, gpar, parent, child, field); \
|
||||
RB_BITS(child, field) &= ~RB_RED_MASK; \
|
||||
if (elm != child) \
|
||||
RB_AUGMENT(elm); \
|
||||
@ -560,7 +572,7 @@ attr void \
|
||||
name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
struct type *parent, struct type *elm) \
|
||||
{ \
|
||||
struct type *sib; \
|
||||
struct type *gpar, *sib; \
|
||||
if (RB_LEFT(parent, field) == elm && \
|
||||
RB_RIGHT(parent, field) == elm) { \
|
||||
RB_BITS(parent, field) &= ~RB_RED_MASK; \
|
||||
@ -570,6 +582,7 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
return; \
|
||||
} \
|
||||
do { \
|
||||
gpar = RB_PARENT(parent, field); \
|
||||
if (RB_LEFT(parent, field) == elm) { \
|
||||
if (!RB_RED_LEFT(parent, field)) { \
|
||||
RB_FLIP_LEFT(parent, field); \
|
||||
@ -588,7 +601,7 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
continue; \
|
||||
case RB_RED_R: \
|
||||
elm = RB_LEFT(sib, field); \
|
||||
RB_ROTATE_RIGHT(head, sib, elm, field); \
|
||||
RB_ROTATE_RIGHT(sib, elm, field); \
|
||||
if (RB_RED_LEFT(elm, field)) \
|
||||
RB_FLIP_ALL(parent, field); \
|
||||
else \
|
||||
@ -613,7 +626,7 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
elm = sib; \
|
||||
break; \
|
||||
} \
|
||||
RB_ROTATE_LEFT(head, parent, elm, field); \
|
||||
RB_ROTATE_LEFT(parent, elm, field); \
|
||||
} else { \
|
||||
if (!RB_RED_RIGHT(parent, field)) { \
|
||||
RB_FLIP_RIGHT(parent, field); \
|
||||
@ -632,7 +645,7 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
continue; \
|
||||
case RB_RED_L: \
|
||||
elm = RB_RIGHT(sib, field); \
|
||||
RB_ROTATE_LEFT(head, sib, elm, field); \
|
||||
RB_ROTATE_LEFT(sib, elm, field); \
|
||||
if (RB_RED_RIGHT(elm, field)) \
|
||||
RB_FLIP_ALL(parent, field); \
|
||||
else \
|
||||
@ -657,8 +670,10 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
elm = sib; \
|
||||
break; \
|
||||
} \
|
||||
RB_ROTATE_RIGHT(head, parent, elm, field); \
|
||||
RB_ROTATE_RIGHT(parent, elm, field); \
|
||||
} \
|
||||
RB_SET_PARENT(elm, gpar, field); \
|
||||
RB_SWAP_CHILD(head, gpar, parent, elm, field); \
|
||||
if (sib != elm) \
|
||||
RB_AUGMENT(sib); \
|
||||
break; \
|
||||
@ -669,10 +684,10 @@ name##_RB_REMOVE_COLOR(struct name *head, \
|
||||
attr struct type * \
|
||||
name##_RB_REMOVE(struct name *head, struct type *elm) \
|
||||
{ \
|
||||
struct type *child, *old, *parent, *right; \
|
||||
struct type *child, *gpar, *old, *parent, *right; \
|
||||
\
|
||||
old = elm; \
|
||||
parent = RB_PARENT(elm, field); \
|
||||
gpar = parent = RB_PARENT(elm, field); \
|
||||
right = RB_RIGHT(elm, field); \
|
||||
if (RB_LEFT(elm, field) == NULL) \
|
||||
elm = child = right; \
|
||||
@ -695,7 +710,7 @@ name##_RB_REMOVE(struct name *head, struct type *elm) \
|
||||
RB_SET_PARENT(RB_LEFT(old, field), elm, field); \
|
||||
elm->field = old->field; \
|
||||
} \
|
||||
RB_SWAP_CHILD(head, old, elm, field); \
|
||||
RB_SWAP_CHILD(head, gpar, old, elm, field); \
|
||||
if (child != NULL) \
|
||||
RB_SET_PARENT(child, parent, field); \
|
||||
if (parent != NULL) { \
|
||||
|
Loading…
Reference in New Issue
Block a user