ab的压力测试（转）

其中-n代表请求数，-c代表并发数

返回结果:

##首先是apache的版本信息
This is ApacheBench, Version 2.3 <Revision:655654>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.xxx.xxx/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking xxx.xxx.com (be patient)

Server Software:    Apache/2.2.19  ##apache版本
Server Hostname:    vm1.xxx.com  ##请求的机子
Server Port:      80 ##请求端口

Document Path:     /xxx.html
Document Length:    25 bytes ##页面长度

Concurrency Level:   100 ##并发数
Time taken for tests:  0.273 seconds ##共使用了多少时间
Complete requests:   1000  ##请求数
Failed requests:    0  ##失败请求
Write errors:      0
Total transferred:   275000 bytes ##总共传输字节数，包含http的头信息等
HTML transferred:    25000 bytes ##html字节数，实际的页面传递字节数
Requests per second:  3661.60 [#/sec] (mean) ##每秒多少请求，这个是非常重要的参数数值，服务器的吞吐量
Time per request:    27.310 [ms] (mean) ##用户平均请求等待时间
Time per request:    0.273 [ms] (mean, across all concurrent requests) ##服务器平均处理时间，也就是服务器吞吐量的倒数
Transfer rate:     983.34 [Kbytes/sec] received ##每秒获取的数据长度

Connection Times (ms)
       min mean[+/-sd] median  max
Connect:    0  1  2.3   0   16
Processing:   6  25  3.2   25   32
Waiting:    5  24  3.2   25   32
Total:     6  25  4.0   25   48

Percentage of the requests served within a certain time (ms)
 50%   25 ## 50%的请求在25ms内返回
 66%   26 ## 60%的请求在26ms内返回
 75%   26
 80%   26
 90%   27
 95%   31
 98%   38
 99%   43
100%   48 (longest request)

apache的ab工具也算是一种ddos攻击工具