From f7f82b81d2c297a5864dcfd0a205917d3e753aba Mon Sep 17 00:00:00 2001 From: Wang Shilong Date: Fri, 12 Apr 2013 12:12:17 +0000 Subject: [PATCH] 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 Reviewed-by: Miao Xie Reviewed-by: Jan Schmidt Signed-off-by: Josef Bacik --- fs/btrfs/ulist.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++-------- fs/btrfs/ulist.h | 6 ++++++ 2 files changed, 56 insertions(+), 8 deletions(-) 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 @@ 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; diff --git a/fs/btrfs/ulist.h b/fs/btrfs/ulist.h index 21a1963..fb36731 100644 --- a/fs/btrfs/ulist.h +++ b/fs/btrfs/ulist.h @@ -8,6 +8,9 @@ #ifndef __ULIST__ #define __ULIST__ +#include +#include + /* * 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 */ -- 2.7.4