ab是apache自带的一个很好用的压力测试工具，当安装完apache的时候，就可以在bin下面找到ab

1 我们可以模拟100个并发用户，对一个页面发送1000个请求

./ab -n1000 -c100 http://www.baidu.com

 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.zeustech.NET/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking vm1.jianfeng.com (be patient)

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

Document Path:          /a.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)

2 ab也可以运行在windows中，如果在windows下安装apache,就可以在bin下找到ab.exe

直接就可以使用，不用依赖其他的dll

下面是我使用ab.exe 测试新浪一个页面的结果：

C:\Users\nickyjf\Desktop\useful>ab -n1000 -c100 http://sports.sina.com.cn/k/2011-05-24/12095590365.shtml
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 sports.sina.com.cn (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests

Server Software:        Apache/2.0.63
Server Hostname:        sports.sina.com.cn
Server Port:            80

Document Path:          /k/2011-05-24/12095590365.shtml
Document Length:        86680 bytes

Concurrency Level:      100
Time taken for tests:   66.453 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      87135790 bytes
HTML transferred:       86680000 bytes
Requests per second:    15.05 [#/sec] (mean)
Time per request:       6645.294 [ms] (mean)
Time per request:       66.453 [ms] (mean, across all concurrent requests)
Transfer rate:          1280.51 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        1   56 398.3      2    3003
Processing:    89 6331 2603.7   6293   14626
Waiting:        2 1748 1485.9   1590    6284
Total:         90 6388 2615.0   6302   14627

Percentage of the requests served within a certain time (ms)
  50%   6302
  66%   7121
  75%   8435
  80%   9193
  90%   9231
  95%   9385
  98%  11549
  99%  12459
100%  14627 (longest request)

3 apache的ab工具也算是一种ddos攻击工具