net: Convert TCP & DCCP hash tables to use RCU / hlist_nulls
RCU was added to UDP lookups, using a fast infrastructure :
- sockets kmem_cache use SLAB_DESTROY_BY_RCU and dont pay the
price of call_rcu() at freeing time.
- hlist_nulls permits to use few memory barriers.
This patch uses same infrastructure for TCP/DCCP established
and timewait sockets.
Thanks to SLAB_DESTROY_BY_RCU, no slowdown for applications
using short lived TCP connections. A followup patch, converting
rwlocks to spinlocks will even speedup this case.
__inet_lookup_established() is pretty fast now we dont have to
dirty a contended cache line (read_lock/read_unlock)
Only established and timewait hashtable are converted to RCU
(bind table and listen table are still using traditional locking)
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index be41ebb..fd269cf 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -223,35 +223,65 @@
INET_ADDR_COOKIE(acookie, saddr, daddr)
const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
struct sock *sk;
- const struct hlist_node *node;
+ const struct hlist_nulls_node *node;
/* Optimize here for direct hit, only listening connections can
* have wildcards anyways.
*/
unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
- struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
- rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);
+ unsigned int slot = hash & (hashinfo->ehash_size - 1);
+ struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
- prefetch(head->chain.first);
- read_lock(lock);
- sk_for_each(sk, node, &head->chain) {
+ rcu_read_lock();
+begin:
+ sk_nulls_for_each_rcu(sk, node, &head->chain) {
if (INET_MATCH(sk, net, hash, acookie,
- saddr, daddr, ports, dif))
- goto hit; /* You sunk my battleship! */
+ saddr, daddr, ports, dif)) {
+ if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
+ goto begintw;
+ if (unlikely(!INET_MATCH(sk, net, hash, acookie,
+ saddr, daddr, ports, dif))) {
+ sock_put(sk);
+ goto begin;
+ }
+ goto out;
+ }
}
+ /*
+ * if the nulls value we got at the end of this lookup is
+ * not the expected one, we must restart lookup.
+ * We probably met an item that was moved to another chain.
+ */
+ if (get_nulls_value(node) != slot)
+ goto begin;
+begintw:
/* Must check for a TIME_WAIT'er before going to listener hash. */
- sk_for_each(sk, node, &head->twchain) {
+ sk_nulls_for_each_rcu(sk, node, &head->twchain) {
if (INET_TW_MATCH(sk, net, hash, acookie,
- saddr, daddr, ports, dif))
- goto hit;
+ saddr, daddr, ports, dif)) {
+ if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) {
+ sk = NULL;
+ goto out;
+ }
+ if (unlikely(!INET_TW_MATCH(sk, net, hash, acookie,
+ saddr, daddr, ports, dif))) {
+ sock_put(sk);
+ goto begintw;
+ }
+ goto out;
+ }
}
+ /*
+ * if the nulls value we got at the end of this lookup is
+ * not the expected one, we must restart lookup.
+ * We probably met an item that was moved to another chain.
+ */
+ if (get_nulls_value(node) != slot)
+ goto begintw;
sk = NULL;
out:
- read_unlock(lock);
+ rcu_read_unlock();
return sk;
-hit:
- sock_hold(sk);
- goto out;
}
EXPORT_SYMBOL_GPL(__inet_lookup_established);
@@ -272,14 +302,14 @@
struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
struct sock *sk2;
- const struct hlist_node *node;
+ const struct hlist_nulls_node *node;
struct inet_timewait_sock *tw;
prefetch(head->chain.first);
write_lock(lock);
/* Check TIME-WAIT sockets first. */
- sk_for_each(sk2, node, &head->twchain) {
+ sk_nulls_for_each(sk2, node, &head->twchain) {
tw = inet_twsk(sk2);
if (INET_TW_MATCH(sk2, net, hash, acookie,
@@ -293,7 +323,7 @@
tw = NULL;
/* And established part... */
- sk_for_each(sk2, node, &head->chain) {
+ sk_nulls_for_each(sk2, node, &head->chain) {
if (INET_MATCH(sk2, net, hash, acookie,
saddr, daddr, ports, dif))
goto not_unique;
@@ -306,7 +336,7 @@
inet->sport = htons(lport);
sk->sk_hash = hash;
WARN_ON(!sk_unhashed(sk));
- __sk_add_node(sk, &head->chain);
+ __sk_nulls_add_node_rcu(sk, &head->chain);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
write_unlock(lock);
@@ -338,7 +368,7 @@
void __inet_hash_nolisten(struct sock *sk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
- struct hlist_head *list;
+ struct hlist_nulls_head *list;
rwlock_t *lock;
struct inet_ehash_bucket *head;
@@ -350,7 +380,7 @@
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
write_lock(lock);
- __sk_add_node(sk, list);
+ __sk_nulls_add_node_rcu(sk, list);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
write_unlock(lock);
}
@@ -400,13 +430,15 @@
local_bh_disable();
inet_listen_wlock(hashinfo);
lock = &hashinfo->lhash_lock;
+ if (__sk_del_node_init(sk))
+ sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
} else {
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
write_lock_bh(lock);
+ if (__sk_nulls_del_node_init_rcu(sk))
+ sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
}
- if (__sk_del_node_init(sk))
- sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
write_unlock_bh(lock);
out:
if (sk->sk_state == TCP_LISTEN)