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authorEric Dumazet <edumazet@google.com>2015-10-02 11:43:35 -0700
committerDavid S. Miller <davem@davemloft.net>2015-10-03 04:32:43 -0700
commitca6fb06518836ef9b65dc0aac02ff97704d52a05 (patch)
tree3fbe433aac9dcf1cae49e6715ced18bd3505d811 /net/ipv6
parent1b33bc3e9e903f7293f7dfe80a875b2a5d0305aa (diff)
tcp: attach SYNACK messages to request sockets instead of listener
If a listen backlog is very big (to avoid syncookies), then the listener sk->sk_wmem_alloc is the main source of false sharing, as we need to touch it twice per SYNACK re-transmit and TX completion. (One SYN packet takes listener lock once, but up to 6 SYNACK are generated) By attaching the skb to the request socket, we remove this source of contention. Tested: listen(fd, 10485760); // single listener (no SO_REUSEPORT) 16 RX/TX queue NIC Sustain a SYNFLOOD attack of ~320,000 SYN per second, Sending ~1,400,000 SYNACK per second. Perf profiles now show listener spinlock being next bottleneck. 20.29% [kernel] [k] queued_spin_lock_slowpath 10.06% [kernel] [k] __inet_lookup_established 5.12% [kernel] [k] reqsk_timer_handler 3.22% [kernel] [k] get_next_timer_interrupt 3.00% [kernel] [k] tcp_make_synack 2.77% [kernel] [k] ipt_do_table 2.70% [kernel] [k] run_timer_softirq 2.50% [kernel] [k] ip_finish_output 2.04% [kernel] [k] cascade Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/tcp_ipv6.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index a215614cfb2b..3d18571811c5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -438,7 +438,8 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
struct flowi *fl,
struct request_sock *req,
u16 queue_mapping,
- struct tcp_fastopen_cookie *foc)
+ struct tcp_fastopen_cookie *foc,
+ bool attach_req)
{
struct inet_request_sock *ireq = inet_rsk(req);
struct ipv6_pinfo *np = inet6_sk(sk);
@@ -451,7 +452,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
IPPROTO_TCP)) == NULL)
goto done;
- skb = tcp_make_synack(sk, dst, req, foc);
+ skb = tcp_make_synack(sk, dst, req, foc, attach_req);
if (skb) {
__tcp_v6_send_check(skb, &ireq->ir_v6_loc_addr,