调整TCP的缓冲区及对TCP连接状态进行调整及TCP状态队列
后两个之前有调整，这次只高速了TCP的缓冲区
Increasing the TCP send and receive buffers will increase the performance a lot if (and only if) you have a lot of large files to send.
增加TCP 发送和接收缓冲区对性能有很大的提高，在你有大文件发送的情况下
net.ipv4.tcp_wmem = 4096 65536 524288
net.core.wmem_max = 1048576
If you have a lot of large file uploads, increasing the receive buffers will help.
如果你有大文件上传，增大接收缓冲区对给你带来帮助
net.ipv4.tcp_rmem = 4096 87380 524288
net.core.rmem_max = 1048576
# These ensure that TIME_WAIT ports either get reused or closed fast.
以下参数确保TIME_WAIT 快速关闭
net.ipv4.tcp_fin_timeout = 1 ##打开fin_wait 快速关闭参数
net.ipv4.tcp_tw_recycle = 1 ##快速回收fin_wait参数
net.ipv4.tcp_tw_recycle = 1 ##快速回收fin_wait参数
设置内核TCP的相关参数
# TCP memory
net.core.rmem_max = 16777216 ##内核最大接收缓冲 16M
net.core.rmem_default = 16777216 ##内核?认接收缓冲 16M
net.core.netdev_max_backlog = 262144 ##2M
net.core.somaxconn = 262144 ##2M
net.core.rmem_default = 16777216 ##内核?认接收缓冲 16M
net.core.netdev_max_backlog = 262144 ##2M
net.core.somaxconn = 262144 ##2M
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net.ipv4.tcp_syncookies = 1 ##打开SYN_COOKIE
net.ipv4.tcp_max_orphans = 262144 ##2M
net.ipv4.tcp_max_syn_backlog = 262144 ##SYN 队列大小 2M
net.ipv4.tcp_synack_retries = 2 ##SYN_ACK重试次数 2秒
net.ipv4.tcp_syn_retries = 2 ## SYN 重试次数 2秒
net.ipv4.tcp_max_orphans = 262144 ##2M
net.ipv4.tcp_max_syn_backlog = 262144 ##SYN 队列大小 2M
net.ipv4.tcp_synack_retries = 2 ##SYN_ACK重试次数 2秒
net.ipv4.tcp_syn_retries = 2 ## SYN 重试次数 2秒
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# you shouldn’t be using conntrack on a heavily loaded server anyway, but these are
# suitably high for our uses, insuring that if conntrack gets turned on, the box doesn’t die
如果用到IPTABLES 同样要增长ip_conntrack 的大小，这个是iptables 所管理的状态数目
net.ipv4.ip_conntrack_max = 1048576
net.ipv4.netfilter.ip_conntrack_max = 1048576
net.ipv4.netfilter.ip_conntrack_max = 1048576
