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authorPatrick McHardy <kaber@trash.net>2007-07-07 22:37:38 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2007-07-10 22:18:15 -0700
commit7ae7730fd6d98be1afe8ad9ea77813de607ec970 (patch)
treecb0cebe96de34a5d6116e4f76377e6ef4ca43547 /net
parentec59a1110aee6846adada8979915cacae64042ce (diff)
[NETFILTER]: nf_conntrack: early_drop improvement
When the maximum number of conntrack entries is reached and a new one needs to be allocated, conntrack tries to drop an unassured connection from the same hash bucket the new conntrack would hash to. Since with a properly sized hash the average number of entries per bucket is 1, the chances of actually finding one are not very good. This patch makes it walk the hash until a minimum number of 8 entries are checked. Based on patch by Vasily Averin <vvs@sw.ru>. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nf_conntrack_core.c22
1 files changed, 15 insertions, 7 deletions
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index d1fc019760a..472396dac05 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -377,21 +377,30 @@ nf_conntrack_tuple_taken(const struct nf_conntrack_tuple *tuple,
}
EXPORT_SYMBOL_GPL(nf_conntrack_tuple_taken);
+#define NF_CT_EVICTION_RANGE 8
+
/* There's a small race here where we may free a just-assured
connection. Too bad: we're in trouble anyway. */
-static int early_drop(struct hlist_head *chain)
+static int early_drop(unsigned int hash)
{
/* Use oldest entry, which is roughly LRU */
struct nf_conntrack_tuple_hash *h;
struct nf_conn *ct = NULL, *tmp;
struct hlist_node *n;
+ unsigned int i, cnt = 0;
int dropped = 0;
read_lock_bh(&nf_conntrack_lock);
- hlist_for_each_entry(h, n, chain, hnode) {
- tmp = nf_ct_tuplehash_to_ctrack(h);
- if (!test_bit(IPS_ASSURED_BIT, &tmp->status))
- ct = tmp;
+ for (i = 0; i < nf_conntrack_htable_size; i++) {
+ hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode) {
+ tmp = nf_ct_tuplehash_to_ctrack(h);
+ if (!test_bit(IPS_ASSURED_BIT, &tmp->status))
+ ct = tmp;
+ cnt++;
+ }
+ if (ct || cnt >= NF_CT_EVICTION_RANGE)
+ break;
+ hash = (hash + 1) % nf_conntrack_htable_size;
}
if (ct)
atomic_inc(&ct->ct_general.use);
@@ -425,8 +434,7 @@ struct nf_conn *nf_conntrack_alloc(const struct nf_conntrack_tuple *orig,
if (nf_conntrack_max
&& atomic_read(&nf_conntrack_count) > nf_conntrack_max) {
unsigned int hash = hash_conntrack(orig);
- /* Try dropping from this hash chain. */
- if (!early_drop(&nf_conntrack_hash[hash])) {
+ if (!early_drop(hash)) {
atomic_dec(&nf_conntrack_count);
if (net_ratelimit())
printk(KERN_WARNING