apache server-status问题

服务器apache总是占用99.9%的cpu 看了一下server-status发现几个疑问：
Parent Server Generation: 0
Server uptime: 23 hours 55 minutes 32 seconds
Total accesses: 5196105 - Total Traffic: 22.7 GB
CPU Usage: u99.9 s8 cu0 cs0 - .125% CPU load
60.3 requests/sec - 276.7 kB/second - 4696 B/request
85 requests currently being processed, 171 idle workers

Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process

Srv PID Acc M CPU  SS Req Conn Child Slot Client VHost Request

1800个请求中没有pid的1475个M都是"." Open slot with no current process
有pid的才325个 但是其中"_" Waiting for Connection有155个

感觉apache进程堵塞？ 谁能指点一下如何进一步分析

apache 2.0.59
<IfModule worker.c>
StartServers         5
ServerLimit         32
ThreadLimit        128
MaxClients        4096
MinSpareThreads    128
MaxSpareThreads    512
ThreadsPerChild    128
MaxRequestsPerChild  50
</IfModule>

运行有php 4.4.4（5.2.5也不行） memcacheclient 2.2.1 jboss4.0.3sp1