充分发挥nginx的性能，对系统参数做一些调整：
net.ipv4.ip_forward =0
net.ipv4.conf.default.rp_filter =1
net.ipv4.conf.accept_source_route =0
kernel.sysrq = 0
kernel.core_user_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax=65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.tcp_max_tw_buckers = 6000
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp.wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.netdev_max_backlog = 262144
net.core.somaxconn = 252144
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_timestamps =0
net.ipv4.tcp_syncack_retries = 1
net.ipv4.tcp_syn_retries =1
net.ipv4.tcp_tw_recycle=1
net.ipv4.tcp_tw_reuse =1
net.ipv4.tcp_mem= 9450000 915000000 927000000
net.ipv4.tcp_fin_timeout = 1
net.ipv4.tcp_keepalive_time= 30
net.ipv4.ip_local_port_range = 1024 65000
