Commit f7f82b81 authored by Wang Shilong's avatar Wang Shilong Committed by Josef Bacik

Btrfs: add a rb_tree to improve performance of ulist search

Walking backref tree and btrfs quota rely on ulist very much.
This patch tries to use rb_tree to speed up search time.

The original code always checks whether an element
exists before adding a new element, however it costs O(n).

I try to add a rb_tree in the ulist,this is only used to speed up
search. I also do some measurements with quota enabled.

fsstress -p 4 -n 10000

Without this path:
real    0m51.058s       2m4.745s        1m28.222s       1m5.137s
user    0m0.035s        0m0.041s        0m0.105s        0m0.100s
sys     0m12.009s       0m11.246s       0m10.901s       0m10.999s       0m11.287s

With this path:
real    0m55.295s       0m50.960s       1m2.214s        0m48.273s
user    0m0.053s        0m0.095s        0m0.135s        0m0.107s
sys     0m7.766s        0m6.013s        0m6.319s        0m6.030s        0m6.532s

After applying the patch,the execute time is down by ~42%.(11.287s->6.532s)
Signed-off-by: default avatarWang Shilong <wangsl-fnst@cn.fujitsu.com>
Reviewed-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Reviewed-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent c2c71324
......@@ -53,6 +53,7 @@ void ulist_init(struct ulist *ulist)
ulist->nnodes = 0;
ulist->nodes = ulist->int_nodes;
ulist->nodes_alloced = ULIST_SIZE;
ulist->root = RB_ROOT;
}
EXPORT_SYMBOL(ulist_init);
......@@ -72,6 +73,7 @@ void ulist_fini(struct ulist *ulist)
if (ulist->nodes_alloced > ULIST_SIZE)
kfree(ulist->nodes);
ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
ulist->root = RB_ROOT;
}
EXPORT_SYMBOL(ulist_fini);
......@@ -123,6 +125,45 @@ void ulist_free(struct ulist *ulist)
}
EXPORT_SYMBOL(ulist_free);
static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
{
struct rb_node *n = ulist->root.rb_node;
struct ulist_node *u = NULL;
while (n) {
u = rb_entry(n, struct ulist_node, rb_node);
if (u->val < val)
n = n->rb_right;
else if (u->val > val)
n = n->rb_left;
else
return u;
}
return NULL;
}
static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
{
struct rb_node **p = &ulist->root.rb_node;
struct rb_node *parent = NULL;
struct ulist_node *cur = NULL;
while (*p) {
parent = *p;
cur = rb_entry(parent, struct ulist_node, rb_node);
if (cur->val < ins->val)
p = &(*p)->rb_right;
else if (cur->val > ins->val)
p = &(*p)->rb_left;
else
return -EEXIST;
}
rb_link_node(&ins->rb_node, parent, p);
rb_insert_color(&ins->rb_node, &ulist->root);
return 0;
}
/**
* ulist_add - add an element to the ulist
* @ulist: ulist to add the element to
......@@ -151,14 +192,13 @@ int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
u64 *old_aux, gfp_t gfp_mask)
{
int i;
for (i = 0; i < ulist->nnodes; ++i) {
if (ulist->nodes[i].val == val) {
if (old_aux)
*old_aux = ulist->nodes[i].aux;
return 0;
}
int ret = 0;
struct ulist_node *node = NULL;
node = ulist_rbtree_search(ulist, val);
if (node) {
if (old_aux)
*old_aux = node->aux;
return 0;
}
if (ulist->nnodes >= ulist->nodes_alloced) {
......@@ -187,6 +227,8 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
}
ulist->nodes[ulist->nnodes].val = val;
ulist->nodes[ulist->nnodes].aux = aux;
ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);
BUG_ON(ret);
++ulist->nnodes;
return 1;
......
......@@ -8,6 +8,9 @@
#ifndef __ULIST__
#define __ULIST__
#include <linux/list.h>
#include <linux/rbtree.h>
/*
* ulist is a generic data structure to hold a collection of unique u64
* values. The only operations it supports is adding to the list and
......@@ -34,6 +37,7 @@ struct ulist_iterator {
struct ulist_node {
u64 val; /* value to store */
u64 aux; /* auxiliary value saved along with the val */
struct rb_node rb_node; /* used to speed up search */
};
struct ulist {
......@@ -54,6 +58,8 @@ struct ulist {
*/
struct ulist_node *nodes;
struct rb_root root;
/*
* inline storage space for the first ULIST_SIZE entries
*/
......
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