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: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c
index ddc61ca..7b417e2 100644
--- a/fs/btrfs/ulist.c
+++ b/fs/btrfs/ulist.c
@@ -53,6 +53,7 @@
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 @@
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 @@
}
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_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 @@
}
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;