参考：http://www.centoscn.com/CentOS/Intermediate/2014/0318/2594.html
目前服务器内存为64GB
把参数添加到/etc/sysctl.conf中，然后执行sysctl -p使参数生效，永久生效
net.ipv4.tcp_syn_retries = 1
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_keepalive_time = 600
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.tcp_keepalive_intvl =15
net.ipv4.tcp_retries2 = 5
net.ipv4.tcp_fin_timeout = 2
net.ipv4.tcp_max_tw_buckets = 36000
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_max_orphans = 32768
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_wmem = 51200 131072 204800
net.ipv4.tcp_rmem = 51200 131072 204800
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.ip_conntrack_max = 65536
net.core.somaxconn = 16384
net.core.netdev_max_backlog = 16384
# net.ipv4.tcp_mem = 786432 1048576 1572864
#net.ipv4.netfilter.ip_conntrack_max=65536
#net.ipv4.netfilter.ip_conntrack_tcp_timeout_established=180