fib_trie: /proc/net/route performance improvement

Use key/offset caching to change /proc/net/route (use by iputils route)
from O(n^2) to O(n). This improves performance from 30sec with 160,000
routes to 1sec.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 82 insertions, 11 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 2d895274b7f8..1ff446d0fa8b 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2459,6 +2459,84 @@ static const struct file_operations fib_trie_fops = {
         .release = seq_release_net,
 };
 
+struct fib_route_iter {
+        struct seq_net_private p;
+        struct trie *main_trie;
+        loff_t  pos;
+        t_key   key;
+};
+
+static struct leaf *fib_route_get_idx(struct fib_route_iter *iter, loff_t pos)
+{
+        struct leaf *l = NULL;
+        struct trie *t = iter->main_trie;
+
+        /* use cache location of last found key */
+        if (iter->pos > 0 && pos >= iter->pos && (l = fib_find_node(t, iter->key)))
+                pos -= iter->pos;
+        else {
+                iter->pos = 0;
+                l = trie_firstleaf(t);
+        }
+
+        while (l && pos-- > 0) {
+                iter->pos++;
+                l = trie_nextleaf(l);
+        }
+
+        if (l)
+                iter->key = pos;        /* remember it */
+        else
+                iter->pos = 0;          /* forget it */
+
+        return l;
+}
+
+static void *fib_route_seq_start(struct seq_file *seq, loff_t *pos)
+        __acquires(RCU)
+{
+        struct fib_route_iter *iter = seq->private;
+        struct fib_table *tb;
+
+        rcu_read_lock();
+        tb = fib_get_table(iter->p.net, RT_TABLE_MAIN);
+        if (!tb)
+                return NULL;
+
+        iter->main_trie = (struct trie *) tb->tb_data;
+        if (*pos == 0)
+                return SEQ_START_TOKEN;
+        else
+                return fib_route_get_idx(iter, *pos - 1);
+}
+
+static void *fib_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+        struct fib_route_iter *iter = seq->private;
+        struct leaf *l = v;
+
+        ++*pos;
+        if (v == SEQ_START_TOKEN) {
+                iter->pos = 0;
+                l = trie_firstleaf(iter->main_trie);
+        } else {
+                iter->pos++;
+                l = trie_nextleaf(l);
+        }
+
+        if (l)
+                iter->key = l->key;
+        else
+                iter->pos = 0;
+        return l;
+}
+
+static void fib_route_seq_stop(struct seq_file *seq, void *v)
+        __releases(RCU)
+{
+        rcu_read_unlock();
+}
+
 static unsigned fib_flag_trans(int type, __be32 mask, const struct fib_info *fi)
 {
         static unsigned type2flags[RTN_MAX + 1] = {
@@ -2482,7 +2560,6 @@ static unsigned fib_flag_trans(int type, __be32 mask, const struct fib_info *fi)
  */
 static int fib_route_seq_show(struct seq_file *seq, void *v)
 {
-        const struct fib_trie_iter *iter = seq->private;
         struct leaf *l = v;
         struct leaf_info *li;
         struct hlist_node *node;
@@ -2494,12 +2571,6 @@ static int fib_route_seq_show(struct seq_file *seq, void *v)
                 return 0;
         }
 
-        if (iter->trie == iter->trie_local)
-                return 0;
-
-        if (IS_TNODE(l))
-                return 0;
-
         hlist_for_each_entry_rcu(li, node, &l->list, hlist) {
                 struct fib_alias *fa;
                 __be32 mask, prefix;
@@ -2542,16 +2613,16 @@ static int fib_route_seq_show(struct seq_file *seq, void *v)
 }
 
 static const struct seq_operations fib_route_seq_ops = {
-        .start  = fib_trie_seq_start,
-        .next   = fib_trie_seq_next,
-        .stop   = fib_trie_seq_stop,
+        .start  = fib_route_seq_start,
+        .next   = fib_route_seq_next,
+        .stop   = fib_route_seq_stop,
         .show   = fib_route_seq_show,
 };
 
 static int fib_route_seq_open(struct inode *inode, struct file *file)
 {
         return seq_open_net(inode, file, &fib_route_seq_ops,
-                            sizeof(struct fib_trie_iter));
+                            sizeof(struct fib_route_iter));
 }
 
 static const struct file_operations fib_route_fops = {