tcp/dccp: remove twchain

TCP listener refactoring, part 3 :

Our goal is to hash SYN_RECV sockets into main ehash for fast lookup,
and parallel SYN processing.

Current inet_ehash_bucket contains two chains, one for ESTABLISH (and
friend states) sockets, another for TIME_WAIT sockets only.

As the hash table is sized to get at most one socket per bucket, it
makes little sense to have separate twchain, as it makes the lookup
slightly more complicated, and doubles hash table memory usage.

If we make sure all socket types have the lookup keys at the same
offsets, we can use a generic and faster lookup. It turns out TIME_WAIT
and ESTABLISHED sockets already have common lookup fields for IPv4.

[ INET_TW_MATCH() is no longer needed ]

I'll provide a follow-up to factorize IPv6 lookup as well, to remove
INET6_TW_MATCH()

This way, SYN_RECV pseudo sockets will be supported the same.

A new sock_gen_put() helper is added, doing either a sock_put() or
inet_twsk_put() [ and will support SYN_RECV later ].

Note this helper should only be called in real slow path, when rcu
lookup found a socket that was moved to another identity (freed/reused
immediately), but could eventually be used in other contexts, like
sock_edemux()

Before patch :

dmesg | grep "TCP established"

TCP established hash table entries: 524288 (order: 11, 8388608 bytes)

After patch :

TCP established hash table entries: 524288 (order: 10, 4194304 bytes)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 7cf8d23..3f3e48c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -156,7 +156,7 @@ typedef __u64 __bitwise __addrpair;
  */
 struct sock_common {
 	/* skc_daddr and skc_rcv_saddr must be grouped on a 8 bytes aligned
-	 * address on 64bit arches : cf INET_MATCH() and INET_TW_MATCH()
+	 * address on 64bit arches : cf INET_MATCH()
 	 */
 	union {
 		__addrpair	skc_addrpair;
@@ -301,6 +301,8 @@ struct sock {
 #define sk_dontcopy_end		__sk_common.skc_dontcopy_end
 #define sk_hash			__sk_common.skc_hash
 #define sk_portpair		__sk_common.skc_portpair
+#define sk_num			__sk_common.skc_num
+#define sk_dport		__sk_common.skc_dport
 #define sk_addrpair		__sk_common.skc_addrpair
 #define sk_daddr		__sk_common.skc_daddr
 #define sk_rcv_saddr		__sk_common.skc_rcv_saddr
@@ -1653,6 +1655,10 @@ static inline void sock_put(struct sock *sk)
 	if (atomic_dec_and_test(&sk->sk_refcnt))
 		sk_free(sk);
 }
+/* Generic version of sock_put(), dealing with all sockets
+ * (TCP_TIMEWAIT, ESTABLISHED...)
+ */
+void sock_gen_put(struct sock *sk);
 
 int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested);