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authorEric Dumazet <edumazet@google.com>2015-10-02 11:43:39 -0700
committerDavid S. Miller <davem@davemloft.net>2015-10-03 04:32:46 -0700
commite994b2f0fb9229aeff5eea9541320bd7b2ca8714 (patch)
tree0caf05649d27830ba0f9548704abbb1ec4b5bb91 /net/ipv4/tcp_ipv4.c
parent92d6f176fdcce1a9c22a59d754c924168fdf2ce4 (diff)
tcp: do not lock listener to process SYN packets
Everything should now be ready to finally allow SYN packets processing without holding listener lock. Tested: 3.5 Mpps SYNFLOOD. Plenty of cpu cycles available. Next bottleneck is the refcount taken on listener, that could be avoided if we remove SLAB_DESTROY_BY_RCU strict semantic for listeners, and use regular RCU. 13.18% [kernel] [k] __inet_lookup_listener 9.61% [kernel] [k] tcp_conn_request 8.16% [kernel] [k] sha_transform 5.30% [kernel] [k] inet_reqsk_alloc 4.22% [kernel] [k] sock_put 3.74% [kernel] [k] tcp_make_synack 2.88% [kernel] [k] ipt_do_table 2.56% [kernel] [k] memcpy_erms 2.53% [kernel] [k] sock_wfree 2.40% [kernel] [k] tcp_v4_rcv 2.08% [kernel] [k] fib_table_lookup 1.84% [kernel] [k] tcp_openreq_init_rwin Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
-rw-r--r--net/ipv4/tcp_ipv4.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ac2ea73e9aaf..34310748a365 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1355,7 +1355,7 @@ static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
}
/* The socket must have it's spinlock held when we get
- * here.
+ * here, unless it is a TCP_LISTEN socket.
*
* We have a potential double-lock case here, so even when
* doing backlog processing we use the BH locking scheme.
@@ -1619,9 +1619,15 @@ process:
if (sk_filter(sk, skb))
goto discard_and_relse;
- sk_incoming_cpu_update(sk);
skb->dev = NULL;
+ if (sk->sk_state == TCP_LISTEN) {
+ ret = tcp_v4_do_rcv(sk, skb);
+ goto put_and_return;
+ }
+
+ sk_incoming_cpu_update(sk);
+
bh_lock_sock_nested(sk);
tcp_sk(sk)->segs_in += max_t(u16, 1, skb_shinfo(skb)->gso_segs);
ret = 0;
@@ -1636,6 +1642,7 @@ process:
}
bh_unlock_sock(sk);
+put_and_return:
sock_put(sk);
return ret;