减少tcp TIME_WAIT 的数量
服务器大量连接，大概2w，不正常的，平时稳定在3，4千而已
netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'
LAST_ACK 6
SYN_RECV 574
ESTABLISHED 46
FIN_WAIT1 1451
FIN_WAIT2 822
SYN_SENT 5
CLOSING 3915
TIME_WAIT 15619
TIME_WAIT 最大，达到了令人发指的地步，
网上搜啊搜，基本上是修改内核，/etc/sysctl.conf
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1 //关键点
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_max_syn_backlog = 8192
net.ipv4.tcp_max_tw_buckets = 5000
net.ipv4.tcp_tw_recycle 可以循环利用，wait也是wait了～
改完以后立马下来了不少
netstat -na|wc -l
7573
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