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Commit 612d6c19 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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[PATCH] radix-tree: direct data 



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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 929f9727

include/linux/radix-tree.h

+3 −2
Original line number Diff line number Diff line
@@ -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);

lib/radix-tree.c

+111 −81
Original line number Diff line number Diff line
@@ -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);