https://maxlv.net/optimize-a-shadowsocks-server/

gistfile1.txt

# /etc/security/limits.conf    
* soft nofile 51200
* hard nofile 51200


ulimit -n 51200



# /etc/sysctl.conf  see BDP
# http://www.lognormal.com/blog/2012/09/27/linux-tcpip-tuning/
net.core.wmem_max = 12582912  
net.core.rmem_max = 12582912  
net.ipv4.tcp_rmem = 10240 87380 12582912  
net.ipv4.tcp_wmem = 10240 87380 12582912  
net.ipv4.ip_local_port_range = 18000    65535  
net.ipv4.netfilter.ip_conntrack_tcp_timeout_time_wait = 1  
net.ipv4.tcp_window_scaling = 1  
net.ipv4.tcp_max_syn_backlog = 3240000  
net.core.somaxconn = 3240000  
net.ipv4.tcp_max_tw_buckets = 1440000  
# bbr?  net.ipv4.tcp_congestion_control = hybla  
net.ipv4.tcp_tw_reuse = 1  
net.ipv4.tcp_fin_timeout = 15  
net.ipv4.tcp_syn_retries = 2  
net.ipv4.tcp_synack_retries = 2  
net.ipv4.tcp_tw_recycle = 1