处理2w多请求后出现卡住(连接连不上)问题

[kimkit]

服务端使用的代码是swoole(1.7.19-rc1)首页的HttpServer，运行环境是virtualbox+ubuntu14.04，ab测试是直接在ubuntu里执行的。

ab测试的结果如下，第一次测试到2w多会卡住，直到超时；立刻进行第二次测试，直接超时（此时包括系统的ssh等都连接不上）；过了一会儿进行第三次测试，结果跟第一次一样。我猜测应该是系统的连接资源没有释放导致的，谁能有详细点的解释？

第一次：

root@ubuntu:~# ab -c 10 -t 30 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1528965 $>
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 5000 requests
Completed 10000 requests
Completed 15000 requests
Completed 20000 requests
apr_pollset_poll: The timeout specified has expired (70007)
Total of 23717 requests completed

第二次：

root@ubuntu:~# ab -c 10 -t 30 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1528965 $>
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)
apr_pollset_poll: The timeout specified has expired (70007)

第三次：

root@ubuntu:~# ab -c 10 -t 30 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1528965 $>
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 5000 requests
Completed 10000 requests
Completed 15000 requests
Completed 20000 requests
apr_pollset_poll: The timeout specified has expired (70007)
Total of 23718 requests completed

[matyhtf]

ab 测试请加-k参数启用长连接，或者 启用 快速回收，否则本地端口会不够用。