From e6308be85afee685347fa3440bed10faaa5d6c1a Mon Sep 17 00:00:00 2001 From: Robert Olsson Date: Tue, 4 Oct 2005 13:01:58 -0700 Subject: [IPV4]: fib_trie root-node expansion The patch below introduces special thresholds to keep root node in the trie large. This gives a flatter tree at the cost of a modest memory increase. Overall it seems to be gain and this was also proposed by one the authors of the paper in recent a seminar. Main table after loading 123 k routes. Aver depth: 3.30 Max depth: 9 Root-node size 12 bits Total size: 4044 kB With the patch: Aver depth: 2.78 Max depth: 8 Root-node size 15 bits Total size: 4150 kB An increase of 8-10% was seen in forwading performance for an rDoS attack. Signed-off-by: Robert Olsson Signed-off-by: David S. Miller --- net/ipv4/fib_trie.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 50c0519cd70d..0093ea08c7f5 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -286,6 +286,8 @@ static inline void check_tnode(const struct tnode *tn) static int halve_threshold = 25; static int inflate_threshold = 50; +static int halve_threshold_root = 15; +static int inflate_threshold_root = 25; static void __alias_free_mem(struct rcu_head *head) @@ -449,6 +451,8 @@ static struct node *resize(struct trie *t, struct tnode *tn) int i; int err = 0; struct tnode *old_tn; + int inflate_threshold_use; + int halve_threshold_use; if (!tn) return NULL; @@ -541,10 +545,17 @@ static struct node *resize(struct trie *t, struct tnode *tn) check_tnode(tn); + /* Keep root node larger */ + + if(!tn->parent) + inflate_threshold_use = inflate_threshold_root; + else + inflate_threshold_use = inflate_threshold; + err = 0; while ((tn->full_children > 0 && 50 * (tn->full_children + tnode_child_length(tn) - tn->empty_children) >= - inflate_threshold * tnode_child_length(tn))) { + inflate_threshold_use * tnode_child_length(tn))) { old_tn = tn; tn = inflate(t, tn); @@ -564,10 +575,18 @@ static struct node *resize(struct trie *t, struct tnode *tn) * node is above threshold. */ + + /* Keep root node larger */ + + if(!tn->parent) + halve_threshold_use = halve_threshold_root; + else + halve_threshold_use = halve_threshold; + err = 0; while (tn->bits > 1 && 100 * (tnode_child_length(tn) - tn->empty_children) < - halve_threshold * tnode_child_length(tn)) { + halve_threshold_use * tnode_child_length(tn)) { old_tn = tn; tn = halve(t, tn); -- cgit v1.2.3-59-g8ed1b