linux服务器，一般都要针对业务，进行内核参数做些优化，主要修改配置文件/etc/sysctl.conf
服务器系统是centos7 内存64G，内核参数如下：
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
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_retries1 = 3
net.ipv4.tcp_retries2 = 5
net.ipv4.tcp_fin_timeout = 10
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_max_tw_buckets = 60000
net.ipv4.tcp_max_orphans = 32768
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_wmem = 4096 16384 13107200
net.ipv4.tcp_rmem = 4096 87380 17476000
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.route.gc_timeout = 100
net.core.somaxconn = 32768
net.core.netdev_max_backlog = 32768
net.nf_conntrack_max = 6553500
net.netfilter.nf_conntrack_max = 6553500
net.netfilter.nf_conntrack_tcp_timeout_established = 180
vm.overcommit_memory = 1
vm.swappiness = 1
fs.file-max = 1024000
内核参数centos6、centos7可以通用，或参考这个服务器初始化脚本：
https://aqzt.com/thread-153-1-1.html
使用这套内核参数，可以避免iptables_nf_conntrack table full问题，kernel: TCP: time wait bucket table overflow等问题。
修改配置文件/etc/sysctl.conf，记得sysctl -p生效！
