ab测试时，-c超过300会出错

一台arm7的mk802主机。运行ubuntu 12.04 desktop
从arm7上发起ab到一台win7上的apache。
执行ab -n 10000 -c 300 http://192.168.1.101/会出错，报：
apr_socket_recv: Connection refused (111)

如果改为-c 100则没问题。

ulimit输出：


********:/etc/init.d# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 6514
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 8912
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 6514
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited