注:本文章是搭建Varnish过程中，参考官方的服务器调优建议。
内核调整，支持4K-8K并发
Edit /etc/sysctl.conf
These are numbers from a highly loaded varnishe serving about 4000-8000 req/s
(details: http://projects.linpro.no/pipermail/varnish-misc/2008-April/001769.html)
net.ipv4.ip_local_port_range = 1024 65536
net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.tcp_rmem=4096 87380 16777216
net.ipv4.tcp_wmem=4096 65536 16777216
net.ipv4.tcp_fin_timeout = 3
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.core.netdev_max_backlog = 30000
net.ipv4.tcp_no_metrics_save=1
net.core.somaxconn = 262144
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2
