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tcp/dccp: do not touch listener sk_refcnt under synflood

Browse source 
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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2016-04-01 08:52:17 -07:00 • committed by David S. Miller
commit 3b24d854cb
10 changed files with 134 additions and 163 deletions
Download patch file Download diff file Expand all files Collapse all files

7
net/dccp/ipv4.c
View file

@ -764,6 +764,7 @@ static int dccp_v4_rcv(struct sk_buff *skb)
{
const struct dccp_hdr *dh;
const struct iphdr *iph;
bool refcounted;
struct sock *sk;
int min_cov;
@ -801,7 +802,7 @@ static int dccp_v4_rcv(struct sk_buff *skb)
lookup:
sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
dh->dccph_sport, dh->dccph_dport);
dh->dccph_sport, dh->dccph_dport, &refcounted);
if (!sk) {
dccp_pr_debug("failed to look up flow ID in table and "
"get corresponding socket\n");
@ -830,6 +831,7 @@ lookup:
goto lookup;
}
sock_hold(sk);
refcounted = true;
nsk = dccp_check_req(sk, skb, req);
if (!nsk) {
reqsk_put(req);
@ -886,7 +888,8 @@ discard_it:
return 0;
discard_and_relse:
sock_put(sk);
if (refcounted)
sock_put(sk);
goto discard_it;
}

7
net/dccp/ipv6.c
View file

@ -642,6 +642,7 @@ discard:
static int dccp_v6_rcv(struct sk_buff *skb)
{
const struct dccp_hdr *dh;
bool refcounted;
struct sock *sk;
int min_cov;
@ -670,7 +671,7 @@ static int dccp_v6_rcv(struct sk_buff *skb)
lookup:
sk = __inet6_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
dh->dccph_sport, dh->dccph_dport,
inet6_iif(skb));
inet6_iif(skb), &refcounted);
if (!sk) {
dccp_pr_debug("failed to look up flow ID in table and "
"get corresponding socket\n");
@ -699,6 +700,7 @@ lookup:
goto lookup;
}
sock_hold(sk);
refcounted = true;
nsk = dccp_check_req(sk, skb, req);
if (!nsk) {
reqsk_put(req);
@ -752,7 +754,8 @@ discard_it:
return 0;
discard_and_relse:
sock_put(sk);
if (refcounted)
sock_put(sk);
goto discard_it;
}