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tcp/dccp: do not touch listener sk_refcnt under synflood

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When a SYNFLOOD targets a non SO_REUSEPORT listener, multiple
cpus contend on sk->sk_refcnt and sk->sk_wmem_alloc changes.

By letting listeners use SOCK_RCU_FREE infrastructure,
we can relax TCP_LISTEN lookup rules and avoid touching sk_refcnt

Note that we still use SLAB_DESTROY_BY_RCU rules for other sockets,
only listeners are impacted by this change.

Peak performance under SYNFLOOD is increased by ~33% :

On my test machine, I could process 3.2 Mpps instead of 2.4 Mpps

Most consuming functions are now skb_set_owner_w() and sock_wfree()
contending on sk->sk_wmem_alloc when cooking SYNACK and freeing them.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2016-04-01 08:52:17 -07:00
committed by David S. Miller
parent 3a5d1c0e7c
commit 3b24d854cb
10 changed files with 134 additions and 163 deletions
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3
net/ipv4/inet_diag.c
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@@ -775,13 +775,12 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb,
for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
struct inet_listen_hashbucket *ilb;
struct hlist_nulls_node *node;
struct sock *sk;
num = 0;
ilb = &hashinfo->listening_hash[i];
spin_lock_bh(&ilb->lock);
sk_nulls_for_each(sk, node, &ilb->head) {
sk_for_each(sk, &ilb->head) {
struct inet_sock *inet = inet_sk(sk);
if (!net_eq(sock_net(sk), net))