本文仅做记录，原文地址：https://cloud.tencent.com/developer/article/1181929
测试机器为腾讯云服务器1核1G内存，swap分区2G，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。
一、系统层面
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_reuseecho 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)