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[PATCH] radix-tree: direct data

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The ability to have height 0 radix trees (a direct pointer to the data item
rather than going through a full node->slot) quietly disappeared with
old-2.6-bkcvs commit ffee171812d51652f9ba284302d9e5c5cc14bdfd.  On 64-bit
machines this causes nearly 600 bytes to be used for every <= 4K file in
pagecache.

Re-introduce this feature, root tags stored in spare ->gfp_mask bits.

Simplify radix_tree_delete's complex tag clearing arrangement (which would
become even more complex) by just falling back to tag clearing functions
(the pagecache radix-tree never uses this path anyway, so the icache
savings will mean it's actually a speedup).

On my 4GB G5, this saves 8MB RAM per kernel kernel source+object tree in
pagecache.

Pagecache lookup, insertion, and removal speed for small files will also be
improved.

This makes RCU radix tree harder, but it's worth it.

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 2006-06-23 02:03:22 -07:00 committed by Linus Torvalds
parent 929f97276b
commit 612d6c19db
2 changed files with 114 additions and 83 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
include/linux/radix-tree.h
View file

@ -23,6 +23,9 @@
#include <linux/preempt.h>
#include <linux/types.h>
#define RADIX_TREE_MAX_TAGS 2
/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
struct radix_tree_root {
unsigned int height;
gfp_t gfp_mask;
@ -45,8 +48,6 @@ do { \
(root)->rnode = NULL; \
} while (0)
#define RADIX_TREE_MAX_TAGS 2
int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);

184
lib/radix-tree.c
View file

@ -74,6 +74,11 @@ struct radix_tree_preload {
};
DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
}
/*
* This assumes that the caller has performed appropriate preallocation, and
* that the caller has pinned this thread of control to the current CPU.
@ -82,9 +87,10 @@ static struct radix_tree_node *
radix_tree_node_alloc(struct radix_tree_root *root)
{
struct radix_tree_node *ret;
gfp_t gfp_mask = root_gfp_mask(root);
ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
if (ret == NULL && !(gfp_mask & __GFP_WAIT)) {
struct radix_tree_preload *rtp;
rtp = &__get_cpu_var(radix_tree_preloads);
@ -152,6 +158,27 @@ static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
return test_bit(offset, node->tags[tag]);
}
static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
{
root->gfp_mask |= (1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
{
root->gfp_mask &= ~(1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear_all(struct radix_tree_root *root)
{
root->gfp_mask &= __GFP_BITS_MASK;
}
static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
{
return root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
}
/*
* Returns 1 if any slot in the node has this tag set.
* Otherwise returns 0.
@ -182,7 +209,6 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
{
struct radix_tree_node *node;
unsigned int height;
char tags[RADIX_TREE_MAX_TAGS];
int tag;
/* Figure out what the height should be. */
@ -195,16 +221,6 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
goto out;
}
/*
* Prepare the tag status of the top-level node for propagation
* into the newly-pushed top-level node(s)
*/
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
tags[tag] = 0;
if (any_tag_set(root->rnode, tag))
tags[tag] = 1;
}
do {
if (!(node = radix_tree_node_alloc(root)))
return -ENOMEM;
@ -214,7 +230,7 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
/* Propagate the aggregated tag info into the new root */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (tags[tag])
if (root_tag_get(root, tag))
tag_set(node, tag, 0);
}
@ -243,8 +259,7 @@ int radix_tree_insert(struct radix_tree_root *root,
int error;
/* Make sure the tree is high enough. */
if ((!index && !root->rnode) ||
index > radix_tree_maxindex(root->height)) {
if (index > radix_tree_maxindex(root->height)) {
error = radix_tree_extend(root, index);
if (error)
return error;
@ -255,7 +270,7 @@ int radix_tree_insert(struct radix_tree_root *root,
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
offset = 0; /* uninitialised var warning */
do {
while (height > 0) {
if (slot == NULL) {
/* Have to add a child node. */
if (!(slot = radix_tree_node_alloc(root)))
@ -273,16 +288,21 @@ int radix_tree_insert(struct radix_tree_root *root,
slot = node->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
} while (height > 0);
}
if (slot != NULL)
return -EEXIST;
BUG_ON(!node);
if (node) {
node->count++;
node->slots[offset] = item;
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
} else {
root->rnode = item;
BUG_ON(root_tag_get(root, 0));
BUG_ON(root_tag_get(root, 1));
}
return 0;
}
@ -295,9 +315,13 @@ static inline void **__lookup_slot(struct radix_tree_root *root,
struct radix_tree_node **slot;
height = root->height;
if (index > radix_tree_maxindex(height))
return NULL;
if (height == 0 && root->rnode)
return (void **)&root->rnode;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
slot = &root->rnode;
@ -368,8 +392,8 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
if (index > radix_tree_maxindex(height))
return NULL;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
while (height > 0) {
int offset;
@ -383,6 +407,10 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
height--;
}
/* set the root's tag bit */
if (slot && !root_tag_get(root, tag))
root_tag_set(root, tag);
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_set);
@ -405,9 +433,8 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
struct radix_tree_node *slot;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
void *ret = NULL;
height = root->height;
if (index > radix_tree_maxindex(height))
@ -432,20 +459,24 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
height--;
}
ret = slot;
if (ret == NULL)
if (slot == NULL)
goto out;
do {
while (pathp->node) {
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;
pathp--;
} while (pathp->node);
}
/* clear the root's tag bit */
if (root_tag_get(root, tag))
root_tag_clear(root, tag);
out:
return ret;
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_clear);
@ -458,9 +489,8 @@ EXPORT_SYMBOL(radix_tree_tag_clear);
*
* Return values:
*
* 0: tag not present
* 1: tag present, set
* -1: tag present, unset
* 0: tag not present or not set
* 1: tag set
*/
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
@ -473,6 +503,13 @@ int radix_tree_tag_get(struct radix_tree_root *root,
if (index > radix_tree_maxindex(height))
return 0;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
if (height == 0)
return 1;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
@ -494,7 +531,7 @@ int radix_tree_tag_get(struct radix_tree_root *root,
int ret = tag_get(slot, tag, offset);
BUG_ON(ret && saw_unset_tag);
return ret ? 1 : -1;
return ret;
}
slot = slot->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
@ -514,8 +551,11 @@ __lookup(struct radix_tree_root *root, void **results, unsigned long index,
unsigned long i;
height = root->height;
if (height == 0)
if (height == 0) {
if (root->rnode && index == 0)
results[nr_found++] = root->rnode;
goto out;
}
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
@ -603,10 +643,16 @@ __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
unsigned int height = root->height;
struct radix_tree_node *slot;
if (height == 0) {
if (root->rnode && index == 0)
results[nr_found++] = root->rnode;
goto out;
}
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
while (height > 0) {
do {
unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
@ -637,7 +683,7 @@ __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
}
shift -= RADIX_TREE_MAP_SHIFT;
slot = slot->slots[i];
}
} while (height > 0);
out:
*next_index = index;
return nr_found;
@ -665,6 +711,10 @@ radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
unsigned long cur_index = first_index;
unsigned int ret = 0;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
while (ret < max_items) {
unsigned int nr_found;
unsigned long next_index; /* Index of next search */
@ -689,7 +739,7 @@ EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
/* try to shrink tree height */
while (root->height > 1 &&
while (root->height > 0 &&
root->rnode->count == 1 &&
root->rnode->slots[0]) {
struct radix_tree_node *to_free = root->rnode;
@ -717,12 +767,8 @@ static inline void radix_tree_shrink(struct radix_tree_root *root)
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
struct radix_tree_path *orig_pathp;
struct radix_tree_node *slot;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
void *ret = NULL;
char tags[RADIX_TREE_MAX_TAGS];
int nr_cleared_tags;
int tag;
int offset;
@ -730,11 +776,17 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
if (index > radix_tree_maxindex(height))
goto out;
slot = root->rnode;
if (height == 0 && root->rnode) {
root_tag_clear_all(root);
root->rnode = NULL;
goto out;
}
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
pathp->node = NULL;
slot = root->rnode;
for ( ; height > 0; height--) {
do {
if (slot == NULL)
goto out;
@ -744,44 +796,22 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
pathp->node = slot;
slot = slot->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
}
height--;
} while (height > 0);
ret = slot;
if (ret == NULL)
if (slot == NULL)
goto out;
orig_pathp = pathp;
/*
* Clear all tags associated with the just-deleted item
*/
nr_cleared_tags = 0;
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
tags[tag] = 1;
if (tag_get(pathp->node, tag, pathp->offset)) {
tag_clear(pathp->node, tag, pathp->offset);
if (!any_tag_set(pathp->node, tag)) {
tags[tag] = 0;
nr_cleared_tags++;
}
}
}
for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
for (tag = 0; tag < RADIX_TREE_MAX_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--;
}
}
if (tag_get(pathp->node, tag, pathp->offset))
radix_tree_tag_clear(root, index, tag);
}
/* Now free the nodes we do not need anymore */
for (pathp = orig_pathp; pathp->node; pathp--) {
while (pathp->node) {
pathp->node->slots[pathp->offset] = NULL;
pathp->node->count--;
@ -793,11 +823,15 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
/* Node with zero slots in use so free it */
radix_tree_node_free(pathp->node);
pathp--;
}
root->rnode = NULL;
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
out:
return ret;
return slot;
}
EXPORT_SYMBOL(radix_tree_delete);
@ -808,11 +842,7 @@ EXPORT_SYMBOL(radix_tree_delete);
*/
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
{
struct radix_tree_node *rnode;
rnode = root->rnode;
if (!rnode)
return 0;
return any_tag_set(rnode, tag);
return root_tag_get(root, tag);
}
EXPORT_SYMBOL(radix_tree_tagged);