Apache intermittent crash - HELP!!!

[gary lim <garylim.in@xxxxxxxxx>]

Dear all,

1. I'm using Linux 2.6.16.29 and running on i686 Intel(R) Pentium(R) 4 CPU 3.00GHz GNU/Linux
2. The below info are my machine config and log output
3. Kindly advise how to resolve intermittent apache crash even after performance tuning 

httpd.conf output
# prefork MPM [DEFAULT IF USE=-threads]
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule prefork.c>
    StartServers         2
    MinSpareServers      4
    MaxSpareServers     6
    MaxClients         100
    MaxRequestsPerChild  500
</IfModule>

# worker MPM [DEFAULT IF USE=threads]
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule worker.c>
    StartServers         2
    MaxClients         100
    MinSpareThreads     25
    MaxSpareThreads     75
    ThreadsPerChild     25
    MaxRequestsPerChild  500
</IfModule>



top output
top - 00:09:00 up 157 days, 23:12,  2 users,  load average: 0.67, 0.85, 0.80
Tasks:  47 total,   1 running,  46 sleeping,   0 stopped,   0 zombie
Cpu(s):  8.3% us,  1.4% sy,  0.0% ni, 88.0% id,  2.2% wa,  0.0% hi,  0.0% si
Mem:    917652k total,   858880k used,    58772k free,   142820k buffers
Swap:  1048568k total,    37844k used,  1010724k free,   434476k cached

apache2 error log
*** glibc detected *** /usr/sbin/apache2: double free or corruption (fasttop): 0x08b4faf0 ***
[Tue Dec 15 13:04:22 2009] [error] server reached MaxClients setting, consider raising the MaxClients setting
*** glibc detected *** /usr/sbin/apache2: double free or corruption (fasttop): 0x086a1170 ***
*** glibc detected *** /usr/sbin/apache2: double free or corruption (fasttop): 0x08b48c08 ***
[Wed Dec 16 23:53:07 2009] [warn] child process 1325 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:07 2009] [warn] child process 19910 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:07 2009] [warn] child process 10569 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:07 2009] [warn] child process 16964 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:07 2009] [warn] child process 19718 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:09 2009] [warn] child process 1325 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:09 2009] [warn] child process 19910 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:09 2009] [warn] child process 10569 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:09 2009] [warn] child process 16964 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:09 2009] [warn] child process 19718 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:11 2009] [warn] child process 1325 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:11 2009] [warn] child process 19910 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:11 2009] [warn] child process 10569 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:11 2009] [warn] child process 16964 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:11 2009] [warn] child process 19718 still did not exit, sending a SIGTERM
[Wed Dec 16 23:53:13 2009] [error] child process 1325 still did not exit, sending a SIGKILL
[Wed Dec 16 23:53:13 2009] [error] child process 19910 still did not exit, sending a SIGKILL
[Wed Dec 16 23:53:13 2009] [error] child process 10569 still did not exit, sending a SIGKILL
[Wed Dec 16 23:53:13 2009] [error] child process 16964 still did not exit, sending a SIGKILL


Joomla / PHP / Apache

System Information
PHP built On:	Linux trillian 2.6.16.29-ab1-xenU #1 SMP Sat Sep 23 19:20:15 SGT 2006 i686
Database Version:	5.0.24a-log
PHP Version:	5.1.6-pl4-gentoo
Web Server:	Apache
WebServer to PHP interface:	apache2handler
Joomla! Version:	Joomla! 1.0.15 Stable [ Daytime ] 22 February 2008 23:00 UTC
User Agent:	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)

Mysql
mysql  Ver 14.12 Distrib 5.0.24a, for pc-linux-gnu (i686) using readline 5.1