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Date: Wed, 31 Mar 2010 14:23:30 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Patrick McHardy <kaber@...sh.net>
Cc: Jorrit Kronjee <j.kronjee@...opact.nl>,
netfilter-devel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: [PATCH nf-next-2.6] xt_hashlimit: RCU conversion
xt_hashlimit uses a central lock per hash table and suffers from
contention on some workloads. (Multiqueue NIC or if RPS is enabled)
After RCU conversion, central lock is only used when a writer wants to
add or delete an entry.
For 'readers', updating an existing entry, they use an individual lock
per entry.
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
net/netfilter/xt_hashlimit.c | 115 ++++++++++++++++++---------------
1 file changed, 66 insertions(+), 49 deletions(-)
diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 5470bb0..f245de6 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -81,12 +81,14 @@ struct dsthash_ent {
struct dsthash_dst dst;
/* modified structure members in the end */
+ spinlock_t lock;
unsigned long expires; /* precalculated expiry time */
struct {
unsigned long prev; /* last modification */
u_int32_t credit;
u_int32_t credit_cap, cost;
} rateinfo;
+ struct rcu_head rcu;
};
struct xt_hashlimit_htable {
@@ -143,54 +145,30 @@ dsthash_find(const struct xt_hashlimit_htable *ht,
u_int32_t hash = hash_dst(ht, dst);
if (!hlist_empty(&ht->hash[hash])) {
- hlist_for_each_entry(ent, pos, &ht->hash[hash], node)
- if (dst_cmp(ent, dst))
+ hlist_for_each_entry_rcu(ent, pos, &ht->hash[hash], node)
+ if (dst_cmp(ent, dst)) {
+ spin_lock(&ent->lock);
return ent;
+ }
}
return NULL;
}
-/* allocate dsthash_ent, initialize dst, put in htable and lock it */
-static struct dsthash_ent *
-dsthash_alloc_init(struct xt_hashlimit_htable *ht,
- const struct dsthash_dst *dst)
+static void dsthash_free_rcu(struct rcu_head *head)
{
- struct dsthash_ent *ent;
+ struct dsthash_ent *ent = container_of(head, struct dsthash_ent, rcu);
- /* initialize hash with random val at the time we allocate
- * the first hashtable entry */
- if (!ht->rnd_initialized) {
- get_random_bytes(&ht->rnd, sizeof(ht->rnd));
- ht->rnd_initialized = true;
- }
-
- if (ht->cfg.max && ht->count >= ht->cfg.max) {
- /* FIXME: do something. question is what.. */
- if (net_ratelimit())
- pr_err("max count of %u reached\n", ht->cfg.max);
- return NULL;
- }
-
- ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
- if (!ent) {
- if (net_ratelimit())
- pr_err("cannot allocate dsthash_ent\n");
- return NULL;
- }
- memcpy(&ent->dst, dst, sizeof(ent->dst));
-
- hlist_add_head(&ent->node, &ht->hash[hash_dst(ht, dst)]);
- ht->count++;
- return ent;
+ kmem_cache_free(hashlimit_cachep, ent);
}
-static inline void
-dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
+static void dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
{
- hlist_del(&ent->node);
- kmem_cache_free(hashlimit_cachep, ent);
+ hlist_del_rcu(&ent->node);
+ call_rcu_bh(&ent->rcu, dsthash_free_rcu);
ht->count--;
}
+
+
static void htable_gc(unsigned long htlong);
static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo,
@@ -500,6 +478,49 @@ hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
return 0;
}
+/* allocate dsthash_ent, initialize dst, put in htable and lock it */
+static struct dsthash_ent *
+dsthash_alloc_init(struct xt_hashlimit_htable *ht,
+ const struct dsthash_dst *dst)
+{
+ struct dsthash_ent *ent;
+
+ spin_lock(&ht->lock);
+ /* initialize hash with random val at the time we allocate
+ * the first hashtable entry */
+ if (unlikely(!ht->rnd_initialized)) {
+ get_random_bytes(&ht->rnd, sizeof(ht->rnd));
+ ht->rnd_initialized = true;
+ }
+
+ if (ht->cfg.max && ht->count >= ht->cfg.max) {
+ /* FIXME: do something. question is what.. */
+ if (net_ratelimit())
+ pr_err("max count of %u reached\n", ht->cfg.max);
+ ent = NULL;
+ } else
+ ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
+ if (!ent) {
+ if (net_ratelimit())
+ pr_err("cannot allocate dsthash_ent\n");
+ } else {
+ memcpy(&ent->dst, dst, sizeof(ent->dst));
+ spin_lock_init(&ent->lock);
+
+ ent->expires = jiffies + msecs_to_jiffies(ht->cfg.expire);
+ ent->rateinfo.prev = jiffies;
+ ent->rateinfo.credit = user2credits(ht->cfg.avg *
+ ht->cfg.burst);
+ ent->rateinfo.credit_cap = user2credits(ht->cfg.avg *
+ ht->cfg.burst);
+ ent->rateinfo.cost = user2credits(ht->cfg.avg);
+ spin_lock(&ent->lock);
+ hlist_add_head_rcu(&ent->node, &ht->hash[hash_dst(ht, dst)]);
+ ht->count++;
+ }
+ spin_unlock(&ht->lock);
+ return ent;
+}
static bool
hashlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
@@ -512,22 +533,14 @@ hashlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
if (hashlimit_init_dst(hinfo, &dst, skb, par->thoff) < 0)
goto hotdrop;
- spin_lock_bh(&hinfo->lock);
+ rcu_read_lock_bh();
dh = dsthash_find(hinfo, &dst);
if (dh == NULL) {
dh = dsthash_alloc_init(hinfo, &dst);
if (dh == NULL) {
- spin_unlock_bh(&hinfo->lock);
+ rcu_read_unlock_bh();
goto hotdrop;
}
-
- dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);
- dh->rateinfo.prev = jiffies;
- dh->rateinfo.credit = user2credits(hinfo->cfg.avg *
- hinfo->cfg.burst);
- dh->rateinfo.credit_cap = user2credits(hinfo->cfg.avg *
- hinfo->cfg.burst);
- dh->rateinfo.cost = user2credits(hinfo->cfg.avg);
} else {
/* update expiration timeout */
dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
@@ -537,11 +550,13 @@ hashlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
if (dh->rateinfo.credit >= dh->rateinfo.cost) {
/* below the limit */
dh->rateinfo.credit -= dh->rateinfo.cost;
- spin_unlock_bh(&hinfo->lock);
+ spin_unlock(&dh->lock);
+ rcu_read_unlock_bh();
return !(info->cfg.mode & XT_HASHLIMIT_INVERT);
}
- spin_unlock_bh(&hinfo->lock);
+ spin_unlock(&dh->lock);
+ rcu_read_unlock_bh();
/* default match is underlimit - so over the limit, we need to invert */
return info->cfg.mode & XT_HASHLIMIT_INVERT;
@@ -817,9 +832,11 @@ err1:
static void __exit hashlimit_mt_exit(void)
{
- kmem_cache_destroy(hashlimit_cachep);
xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
unregister_pernet_subsys(&hashlimit_net_ops);
+
+ rcu_barrier_bh();
+ kmem_cache_destroy(hashlimit_cachep);
}
module_init(hashlimit_mt_init);
--
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