如果需要支撑百万级同时在线数，需要对Linux默认内核参数进行调整，我们的典型配置是在/etc/sysctl.conf增加以下内容：
net.ipv4.tcp_max_syn_backlog = 120000
net.core.netdev_max_backlog = 120000
net.core.somaxconn = 12000
net.ipv4.tcp_fin_timeout = 2
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_max_tw_buckets = 1000
net.ipv4.tcp_abort_on_overflow = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_rmem = 4096 8192 32768
net.ipv4.tcp_wmem = 4096 8192 32768
net.core.optmem_max = 8192
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_mem = 3075840 4101120 12303360
net.ipv4.tcp_keepalive_time = 30
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15
net.netfilter.nf_conntrack_tcp_timeout_last_ack = 3
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_syn_retries = 1
net.ipv4.ip_local_port_range = 1024 65535
net.nf_conntrack_max = 6553600
net.netfilter.nf_conntrack_max = 6553500
net.netfilter.nf_conntrack_tcp_timeout_established = 180
