Solved High CPU usage on J2.5 site

I also BTW optimised the MySQL DB, just in case it was lagging.

Hands up who thinks I should just cull my old forum posts?
They go back to 2007. I can eradicate half of them, bringing it down to 3k, without too much loss.

Frankly it's the only thing i can think of that might help

It's not Kunena (at least I'm 95% certain of it). If you would like to send me a PM, I would be happy to sit down and talk with you about the issue.

Altho I did also temporarily block Google and all its bot chums. They seem to visit with a truckoad of needs about every 5 mins.

Something on your site is hoarding the CPU and, as a by-product, is affecting Kunena. I am available to sit down with you, put our heads together, and talk the issues through. If you would like to contact me via Skype or even by telephone, please let me know by PM. I can call you, if you like. I would be happy to.

So here's my current extension list:

-Joostrap template (just minifying it now)
-Advanced Module Mgr
-Xtplorer
-Kunena

I've got caching on and Robots.txt is blocking all bots.

Latest CPU stats:

Jun 16 2012: (final stats)********** All extensions still running
joomla.org.au 4.82 1.22 0.0
Top Process %CPU 149 /usr/bin/php /index.php
Top Process %CPU 126 /usr/bin/php /index.php
Top Process %CPU 124 /usr/bin/php /index.php

Jun 17 2012 (partial stats, 06 hours):********** All extensions turned off, including Kunena
joomla.org.au 0.42 1.03 0.0
Top Process %CPU 27.0 [php]
Top Process %CPU 0.3 httpd [joomla.org.au] [/administrator/templates/bluestork/images/menu/icon-16-mess]
Top Process %CPU 0.1 httpd [joomla.org.au] [/templates/system/css/error.css]

Jun 17 2012 (full day): ********** Kunena turned back on part way thru day
joomla.org.au 1.49 1.00 0.0
Top Process %CPU 93.0 /usr/bin/php /index.php
Top Process %CPU 56.5 /usr/bin/php /index.php
Top Process %CPU 55.0 [php]

Jun 18 2012 (partial stats, 03 hours into the day): ***** Kunena back on
joomla.org.au 1.67 1.27 0.0
Top Process %CPU 69.0 [php]
Top Process %CPU 0.3 httpd [joomla.org.au] [/components/com_kunena/template/default/images/icons/stats.]
Top Process %CPU 0.2 httpd [joomla.org.au] [/media/kunena/avatars/resized/size36/users/avatar63.jpg]

You must remember that if Joomla is turned offline, people just visit one page and go away. If Kunena isn't online, people go to forum and see that it's offline and go away. But if Kunena is online, they probably visit 10-100 pages before leaving your site. And it's the amount of traffic that has the highest impact on your CPU load. So 10 pages vs 1 pages means always more than 10x higher average load.

To me it looks like Kunena isn't the issue. Here's the total resource usage during the last minute or so according to your stats (100% = full load):
All extensions = 482% (bad)
Kunena = 149% (still ok)

Don't look individual process CPU time as they are supposed to be as high as possible to be able to serve pages faster. Look the three numbers above: 1.49 1.00 0.0. Those tell you average CPU load now, during the last few minutes and long average. One CPU = 1.00, except on virtual servers where the number means the time that's allocated to you.

So your other extensions are causing almost 3x load compared to Kunena. It doesn't mean that the extensions are slow, but it points to me that the server resources allocated to your site run out and saturate. The effect is the same as in traffic jam: once the limit is reached everything slows down and take 3-5x more time. If situation doesn't get any better, after a few minutes load gets up to 50-100 and every page load takes something like 30-300 seconds.

Your main issue is that your server just isn't powerful enough to run a busy Joomla site with your current configuration. Part of that can be fixed by optimizing Apache/MySQL configuration and removing all extensions that you really don't need. Also upgrading to Kunena 2.0 should help, as it caches some data and should therefore use less resources.