[文章作者:张宴 本文版本:v1.0 最后修改:2007.07.24 转载请注明出处:http://blog.zyan.cc]

  新增的一组Apache服务器上线以来,我用netstat -an命令发现服务器中有大量状态为TIME-WAIT的TCP连接,于是用/sbin/sysctl -a查看了一下Linux的各项内核参数,并翻阅有关资料,决定修改其中的两项参数,以达到减少TCP连接中TIME-WAIT sockets的目的。

  vi /etc/sysctl.conf
  编辑/etc/sysctl.conf文件,增加三行:
引用
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1

  说明:
  net.ipv4.tcp_syncookies = 1 表示开启SYN Cookies。当出现SYN等待队列溢出时,启用cookies来处理,可防范少量SYN攻击,默认为0,表示关闭;
  net.ipv4.tcp_tw_reuse = 1 表示开启重用。允许将TIME-WAIT sockets重新用于新的TCP连接,默认为0,表示关闭;
  net.ipv4.tcp_tw_recycle = 1 表示开启TCP连接中TIME-WAIT sockets的快速回收,默认为0,表示关闭。

  再执行以下命令,让修改结果立即生效:
  /sbin/sysctl -p

  用以下语句看了一下服务器的TCP状态:
  netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'
  返回结果如下:
  ESTABLISHED 1423
  FIN_WAIT1 1
  FIN_WAIT2 262
  SYN_SENT 1
  TIME_WAIT 962

  效果:处于TIME_WAIT状态的sockets从原来的10000多减少到1000左右。处于SYN_RECV等待处理状态的sockets为0,原来的为50~300。

  附:TCP状态变迁图,见我的另一篇文章《查看Apache并发请求数及其TCP连接状态


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技术大类 » Web服务器 | 评论(45) | 引用(0) | 阅读(62303)
民大学弟
2007-7-24 19:49
张宴大哥不仅在计算机方面颇有造诣,写作水平也不错嘛,加油啊,在新浪干上几年后就可以出书了……呵呵,又一位百万新贵将要诞生!
民大学弟
2007-7-24 20:08
呵呵,如法炮制……不是病毒!
http://learning.sohu.com/s2007/07tzs/?stra=%u5F20%u5BB4
民大学弟
2007-7-25 00:02
张宴大哥,我这几天一直在用纯CSS做二级导航菜单,但老做不成功……呵呵,你那个中南民族大学就业信息网的导航菜单是怎么做的啊,能否在你的博客上专门写一篇文章讲讲制作的过程,讲详细些……或者以word文档的形式将制作的过程写给我,我的邮箱是  be_ok@163.com  写详细些哈,我很笨的,拜托了……你有时间的时候就做,一两个星期内给我答复,我不急……
谢谢你了哈,下次回武汉的话我请客哦grinshyzan
张宴 回复于 2007-7-25 19:48
最近很少做HTML、CSS设计了,对CSS不太感兴趣,给你一篇别人的文章,可以实现那种导航菜单。
http://www.blueidea.com/tech/site/2006/3658.asp
zhangluoer
2007-8-16 13:49
呵,你上面写的三个参数都已经改过了,也没有出现太大的变化,TIME_WAIT一般是ESTABLISHED的10倍左右,甚至更高。
像你上面写的很少见过。
还有什么地方需要优化吗?
张宴 回复于 2007-8-16 14:00
改完后执行/sbin/sysctl -p
zhangluoer
2007-8-16 15:28
我是直接修改的#echo 1 > /proc/sys/net/ipv4/tcp_syncookies的
所以不存在改完后执行/sbin/sysctl -p
另外发现有大量的对:3306端口的访问都处于time_wait状态。
能否确定一下问题的原因,是PHP编程的问题,在链接数据库后没有关系链接,导致大量的链接,还是其它什么原因
3ks
jackbillow
2007-8-31 18:10
张兄,写的不错。
jackbillow
2007-8-31 18:10
smile
大宇
2007-9-3 22:26
不错,照着修改了的确有效的减少了time_wait状态的线程数量

还有个问题,我用top查看,load average: 17.39, 17.10, 16.71
服务器上只有一个httpd服务在跑,怎么负载这么高。
sx
2008-2-21 15:39
关于TCP_TIMEWAIT的问题由来已久,在此补充一下原因吧。都知道tcp的三次握手后建立连接,连接建立后,如果client主动关闭连接,则此连接会被内核回收,而很多时候,比如上面的兄台的PHP程序没有关闭数据库连接,这个时候,server端就无法知道此连接是否还继续有效,也就是,cilent是在组装数据还是已经掉线了呢?那么就进入timewait了。
另外,对于张兄的修改,也补充一下:
net.ipv4.tcp_syncookies = 1,这句是可以的,不提
net.ipv4.tcp_tw_reuse = 1 ,这句对于有些时候,客户端没有真的关闭连接而是在等待发送数据的时候,重用接口会导致数据出错,所以,只是针对HTTP类型可以开启,对于其他长时间连接处理类型,就关上比较稳妥
net.ipv4.tcp_tw_recycle = 1 这句基本上来说用处不大,开启快速回收后,系统还是会一样取系统等待时间,故,要想真的减少timewait时间的话,将内核中的等待时间参数修改为一个合适的值比较妥当,尤其是对于内网机器来说。
goter
2008-6-1 16:49
张大哥,别人老连不上我的BT服务器,用netstat查看,有很多都是close wait
这个是BT服务器配置的问题吗?
storysky
2009-11-3 10:19
你好张老师,我刚接手一台服务器,发现他的time-wait非常多,用了您上面的方法以后发现time-wait少了一些(以前是7000多现在是6000左右),还是很多!
而且ESTABLISHED 一直在600左右,我想问一下有什么好办法解决一下,我的mail 是redsky818@yahoo.com.cn
下面是我的sysctl.conf 的配置和连接状态
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.tcp_max_syn_backlog = 65536
net.core.netdev_max_backlog =  8192
net.ipv4.tcp_max_tw_buckets = 8192
net.core.somaxconn = 32768
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 30
net.ipv4.ip_local_port_range = 1024  65535
kernel.msgmni = 1024
kernel.sem = 250 256000 32 1024
##################################
netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'
TIME_WAIT 6221
FIN_WAIT1 4
ESTABLISHED 615
SYN_RECV 2
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