安装webbench
[root@lnmp webbench-1.5]# make

[root@lnmp webbench-1.5]# make  install


webbench [option]... URL
 -f|--force               Don't wait for reply from server.
 -r|--reload              Send reload request - Pragma: no-cache.
 -t|--time <sec>          Run benchmark for <sec> seconds. Default 30.
-p|--proxy <server:port> Use proxy server for request.
 -c|--clients <n>         Run <n> HTTP clients at once. Default one.
-9|--http09              Use HTTP/0.9 style requests.
 -1|--http10              Use HTTP/1.0 protocol.
 -2|--http11              Use HTTP/1.1 protocol.
 --get                    Use GET request method.
 --head                   Use HEAD request method.
 --options                Use OPTIONS request method.
 --trace                  Use TRACE request method.
 -?|-h|--help             This information.
 -V|--version             Display program version.

测试结果
[root@lnmp ~]# webbench -c 100 -t 30 http://192.168.30.110/index.php
Webbench - Simple Web Benchmark 1.5
Copyright (c) Radim Kolar 1997-2004, GPL Open Source Software.

Benchmarking: GET http://192.168.30.110/index.php
100 clients, running 30 sec.

Speed=14772 pages/min, 12939751 bytes/sec.
Requests: 7386 susceed, 0 failed.

-c 指定连接的用户数
-t  指定连接的时间(s)
根据请求requests可以看到效果

查看负载
top - 00:34:43 up 19 min,  1 user,  load average: 0.00, 0.00, 0.00
Tasks:  75 total,   1 running,  74 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.3%us,  0.0%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:    236536k total,   173644k used,    62892k free,    10228k buffers
Swap:  2031608k total,      604k used,  2031004k free,    77744k cached