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ipv4: tcp: set SOCK_USE_WRITE_QUEUE for ip_send_unicast_reply()

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TCP uses per cpu 'sockets' to send some packets :
- RST packets ( tcp_v4_send_reset()) )
- ACK packets for SYN_RECV and TIMEWAIT sockets

By setting SOCK_USE_WRITE_QUEUE flag, we tell sock_wfree()
to not call sk_write_space() since these internal sockets
do not care.

This gives a small performance improvement, merely by allowing
cpu to properly predict the sock_wfree() conditional branch,
and avoiding one atomic operation.

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 08:52:21 -07:00 committed by David S. Miller
parent 9caad86415
commit a9d6532b56
1 changed files with 1 additions and 0 deletions
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1
net/ipv4/tcp_ipv4.c
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@ -2384,6 +2384,7 @@ static int __net_init tcp_sk_init(struct net *net)
IPPROTO_TCP, net);
if (res)
goto fail;
sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
*per_cpu_ptr(net->ipv4.tcp_sk, cpu) = sk;
}