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| author | Eric Dumazet <edumazet@google.com> | 2015-10-02 11:43:35 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-10-03 04:32:43 -0700 |
| commit | ca6fb06518836ef9b65dc0aac02ff97704d52a05 (patch) | |
| tree | 3fbe433aac9dcf1cae49e6715ced18bd3505d811 /net/ipv4/inet_connection_sock.c | |
| parent | 1b33bc3e9e903f7293f7dfe80a875b2a5d0305aa (diff) | |
| download | linux-0-day-ca6fb06518836ef9b65dc0aac02ff97704d52a05.tar.gz linux-0-day-ca6fb06518836ef9b65dc0aac02ff97704d52a05.tar.xz | |
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/ipv4/inet_connection_sock.c')
| -rw-r--r-- | net/ipv4/inet_connection_sock.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 80904df02187b..099e0ea9242a9 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -628,7 +628,7 @@ static void reqsk_queue_hash_req(struct request_sock *req, * are committed to memory and refcnt initialized. */ smp_wmb(); - atomic_set(&req->rsk_refcnt, 2); + atomic_set(&req->rsk_refcnt, 2 + 1); } void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req, |