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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
Download Patch File Download Diff File Expand all files Collapse all files

40
include/net/inet_hashtables.h
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@@ -100,14 +100,10 @@ struct inet_bind_hashbucket {
/*
* Sockets can be hashed in established or listening table
* We must use different 'nulls' end-of-chain value for listening
* hash table, or we might find a socket that was closed and
* reallocated/inserted into established hash table
*/
#define LISTENING_NULLS_BASE (1U << 29)
struct inet_listen_hashbucket {
spinlock_t lock;
struct hlist_nulls_head head;
struct hlist_head head;
};
/* This is for listening sockets, thus all sockets which possess wildcards. */
@@ -304,14 +300,20 @@ static inline struct sock *__inet_lookup(struct net *net,
struct sk_buff *skb, int doff,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const __be16 dport,
const int dif)
const int dif,
bool *refcounted)
{
u16 hnum = ntohs(dport);
struct sock *sk = __inet_lookup_established(net, hashinfo,
saddr, sport, daddr, hnum, dif);
struct sock *sk;
return sk ? : __inet_lookup_listener(net, hashinfo, skb, doff, saddr,
sport, daddr, hnum, dif);
sk = __inet_lookup_established(net, hashinfo, saddr, sport,
daddr, hnum, dif);
*refcounted = true;
if (sk)
return sk;
*refcounted = false;
return __inet_lookup_listener(net, hashinfo, skb, doff, saddr,
sport, daddr, hnum, dif);
}
static inline struct sock *inet_lookup(struct net *net,
@@ -322,10 +324,13 @@ static inline struct sock *inet_lookup(struct net *net,
const int dif)
{
struct sock *sk;
bool refcounted;
sk = __inet_lookup(net, hashinfo, skb, doff, saddr, sport, daddr,
dport, dif);
dport, dif, &refcounted);
if (sk && !refcounted && !atomic_inc_not_zero(&sk->sk_refcnt))
sk = NULL;
return sk;
}
@@ -333,17 +338,20 @@ static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo,
struct sk_buff *skb,
int doff,
const __be16 sport,
const __be16 dport)
const __be16 dport,
bool *refcounted)
{
struct sock *sk = skb_steal_sock(skb);
const struct iphdr *iph = ip_hdr(skb);
*refcounted = true;
if (sk)
return sk;
else
return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb,
doff, iph->saddr, sport,
iph->daddr, dport, inet_iif(skb));
return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb,
doff, iph->saddr, sport,
iph->daddr, dport, inet_iif(skb),
refcounted);
}
u32 sk_ehashfn(const struct sock *sk);