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[PATCH] radix tree: early termination of tag clearing 

Correctly determine the tags to be cleared in radix_tree_delete() so we
don't keep moving up the tree clearing tags that we don't need to.  For
example, if a tag is simply not set in the deleted item, nor anywhere up
the tree, radix_tree_delete() would attempt to clear it up the entire
height of the tree.

Also, tag_set() was made conditional so as not to dirty too many cachelines
high up in the radix tree.  Instead, put this logic into
radix_tree_tag_set().

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-01-08 01:01:41 -08:00 committed by Linus Torvalds
parent 6e954b9e90
commit d5274261ea
1 changed files with 24 additions and 18 deletions
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42
lib/radix-tree.c
View File

@ -137,18 +137,17 @@ out:
static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
{
if (!test_bit(offset, &node->tags[tag][0]))
__set_bit(offset, &node->tags[tag][0]);
__set_bit(offset, node->tags[tag]);
}
static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
{
__clear_bit(offset, &node->tags[tag][0]);
__clear_bit(offset, node->tags[tag]);
}
static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
{
return test_bit(offset, &node->tags[tag][0]);
return test_bit(offset, node->tags[tag]);
}
/*
@ -375,7 +374,8 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
int offset;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
tag_set(slot, tag, offset);
if (!tag_get(slot, tag, offset))
tag_set(slot, tag, offset);
slot = slot->slots[offset];
BUG_ON(slot == NULL);
shift -= RADIX_TREE_MAP_SHIFT;
@ -435,6 +435,8 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
goto out;
do {
if (!tag_get(pathp->node, tag, pathp->offset))
goto out;
tag_clear(pathp->node, tag, pathp->offset);
if (any_tag_set(pathp->node, tag))
goto out;
@ -695,6 +697,8 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
void *ret = NULL;
char tags[RADIX_TREE_TAGS];
int nr_cleared_tags;
int tag;
int offset;
height = root->height;
if (index > radix_tree_maxindex(height))
@ -705,16 +709,14 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
slot = root->rnode;
for ( ; height > 0; height--) {
int offset;
if (slot == NULL)
goto out;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
pathp[1].offset = offset;
pathp[1].node = slot;
slot = slot->slots[offset];
pathp++;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
pathp->offset = offset;
pathp->node = slot;
slot = slot->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
}
@ -727,24 +729,28 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
/*
* Clear all tags associated with the just-deleted item
*/
memset(tags, 0, sizeof(tags));
do {
int tag;
nr_cleared_tags = 0;
for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
if (tag_get(pathp->node, tag, pathp->offset)) {
tag_clear(pathp->node, tag, pathp->offset);
tags[tag] = 0;
nr_cleared_tags++;
} else
tags[tag] = 1;
}
nr_cleared_tags = RADIX_TREE_TAGS;
for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
if (tags[tag])
continue;
tag_clear(pathp->node, tag, pathp->offset);
if (any_tag_set(pathp->node, tag)) {
tags[tag] = 1;
nr_cleared_tags--;
}
}
pathp--;
} while (pathp->node && nr_cleared_tags);
}
/* Now free the nodes we do not need anymore */
for (pathp = orig_pathp; pathp->node; pathp--) {