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| author |   Robert Olsson <robert.olsson@its.uu.se> | 2005-10-04 13:01:58 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2005-10-04 13:01:58 -0700 |
| commit | e6308be85afee685347fa3440bed10faaa5d6c1a (patch) | |
| tree | 9cb766b5b66f700528722b2e92745a2a6dcc3288 /net/ipv4/fib_trie.c | |
| parent | [IPV6]: Fix infinite loop in udp_v6_get_port(). (diff) | |
| download | linux-dev-e6308be85afee685347fa3440bed10faaa5d6c1a.tar.xz linux-dev-e6308be85afee685347fa3440bed10faaa5d6c1a.zip | |
[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 <robert.olsson@its.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/fib_trie.c')
| -rw-r--r-- | net/ipv4/fib_trie.c | 23 |
1 files changed, 21 insertions, 2 deletions
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); |