https://www.cnblogs.com/sunjianguo/p/8298283.html
停用除SSH外的所有服务，仅保留nginx，优化思路主要包括两个层面：系统层面+nginx层面。
1、调整同时打开文件数量
ulimit -n 20480
2、TCP最大连接数（somaxconn）
echo 10000 > /proc/sys/net/core/somaxconn
3、TCP连接立即回收、回用（recycle、reuse）
echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse
echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle
4、不做TCP洪水抵御
echo 0 > /proc/sys/net/ipv4/tcp_syncookies
也可以直接使用优化后的配置，在/etc/sysctl.conf中加入：
net.core.somaxconn = 20480
net.core.rmem_default = 262144
net.core.wmem_default = 262144
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 4096 16777216
net.ipv4.tcp_wmem = 4096 4096 16777216
net.ipv4.tcp_mem = 786432 2097152 3145728
net.ipv4.tcp_max_syn_backlog = 16384
net.core.netdev_max_backlog = 20000
net.ipv4.tcp_fin_timeout = 15
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_max_orphans = 131072
net.ipv4.tcp_syncookies = 0
使用：sysctl -p 生效
sysctl -p
二、nginx层面
修改nginx配置文件，nginx.conf
增加work_rlimit_nofile和worker_connections数量，并禁用keepalive_timeout。
worker_processes 1;
worker_rlimit_nofile 20000;
events {
use epoll;
worker_connections 20000;
multi_accept on;
}
http {
keepalive_timeout 0;
}
重启nginx
/usr/local/nginx/sbin/nginx -s reload
使用ab压力测试
ab -c 10000 -n 150000 http://127.0.0.1/index.html
测试结果：
This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking 127.0.0.1 (be patient) Completed 15000 requests Completed 30000 requests Completed 45000 requests Completed 60000 requests Completed 75000 requests Completed 90000 requests Completed 105000 requests Completed 120000 requests Completed 135000 requests Completed 150000 requests Finished 150000 requests Server Software: nginx/1.8.0 Server Hostname: 127.0.0.1 Server Port: 80 Document Path: /index.html Document Length: 612 bytes Concurrency Level: 10000 Time taken for tests: 19.185 seconds Complete requests: 150000 Failed requests: 0 Write errors: 0 Total transferred: 131180388 bytes HTML transferred: 95121324 bytes Requests per second: 7818.53 [#/sec] (mean) Time per request: 1279.013 [ms] (mean) Time per request: 0.128 [ms] (mean, across all concurrent requests) Transfer rate: 6677.33 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 650 547.9 522 7427 Processing: 212 519 157.4 496 958 Waiting: 0 404 139.7 380 845 Total: 259 1168 572.1 1066 7961 Percentage of the requests served within a certain time (ms) 50% 1066 66% 1236 75% 1295 80% 1320 90% 1855 95% 2079 98% 2264 99% 2318 100% 7961 (longest request)