emqtt 系统方面参数调优
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（一）执行如下命令
echo 2097152 > /proc/sys/fs/nr_open
ulimit -n 1048576
（二）编辑 /etc/sysctl.conf ，加入如下项
fs.file-max=2097152
fs.nr_open=2097152
net.core.somaxconn=65536
net.ipv4.tcp_max_syn_backlog=16384
net.core.netdev_max_backlog=16384
net.ipv4.ip_local_port_range=1000 65535
net.core.rmem_default=262144
net.core.wmem_default=262144
net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.core.optmem_max=16777216
#net.ipv4.tcp_mem=16777216 16777216 16777216
net.ipv4.tcp_rmem=1024 4096 16777216
net.ipv4.tcp_wmem=1024 4096 16777216
net.nf_conntrack_max=1000000
net.netfilter.nf_conntrack_max=1000000
net.netfilter.nf_conntrack_tcp_timeout_time_wait=30
net.ipv4.tcp_max_tw_buckets=1048576
net.ipv4.tcp_fin_timeout = 15
#然后执行 sysctl -p 生效
（三）编辑 /etc/security/limits.conf文件
/etc/security/limits.conf持久化设置允许用户/进程打开文件句柄数:
* soft nofile 1048576
* hard nofile 1048576
