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From: Alexander Duyck <alexander.h.duyck@redhat.com>
Date: Wed, 31 Dec 2014 10:56:00 -0800
Subject: [PATCH] fib_trie: Optimize fib_find_node
This patch makes use of the same features I made use of for
fib_table_lookup to streamline fib_find_node. The resultant code should be
smaller and run faster than the original.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -892,28 +892,34 @@ static void insert_leaf_info(struct hlis
}
/* rcu_read_lock needs to be hold by caller from readside */
-
static struct tnode *fib_find_node(struct trie *t, u32 key)
{
struct tnode *n = rcu_dereference_rtnl(t->trie);
- int pos = 0;
- while (n && IS_TNODE(n)) {
- if (tkey_sub_equals(n->key, pos, n->pos-pos, key)) {
- pos = n->pos + n->bits;
- n = tnode_get_child_rcu(n,
- tkey_extract_bits(key,
- n->pos,
- n->bits));
- } else
+ while (n) {
+ unsigned long index = get_index(key, n);
+
+ /* This bit of code is a bit tricky but it combines multiple
+ * checks into a single check. The prefix consists of the
+ * prefix plus zeros for the bits in the cindex. The index
+ * is the difference between the key and this value. From
+ * this we can actually derive several pieces of data.
+ * if !(index >> bits)
+ * we know the value is cindex
+ * else
+ * we have a mismatch in skip bits and failed
+ */
+ if (index >> n->bits)
+ return NULL;
+
+ /* we have found a leaf. Prefixes have already been compared */
+ if (IS_LEAF(n))
break;
- }
- /* Case we have found a leaf. Compare prefixes */
- if (n != NULL && IS_LEAF(n) && tkey_equals(key, n->key))
- return n;
+ n = rcu_dereference_rtnl(n->child[index]);
+ }
- return NULL;
+ return n;
}
static void trie_rebalance(struct trie *t, struct tnode *tn)
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