I've been reading a lot on the forums in regards to CPU load time. Especially: http://wordpress.org/support/topic/very-high-cpu-usage?replies=72
However, the solutions of optimizing the DB, disabling plugins etc. are not helping. Neither are Wp-cache or similar, as I am using W3 Total Cache and Varnish. This is resulting in 3000 req/sec in the frontend.
My issue is the backend. When I go to settings->permalinks or primarily edit / add new posts, the load time is around 30 secs and CPU load is 100%. I have monitored SQL queries with the plugin SQL mon but all the queries in total are less than 1 sec.
Therefore I ended up with disabling the function page_rewrite_rules() in wp-includes/rewrite.php. This solved my issue. However, I guess permalinks are not functioning.
My question is - can I disable the page_rewrite_rules() function and update the permalinks with a custom plugin? E.g. with a crontab every 24 hours.
WordPress 3.0, PHP5, Apache2, Debian
+1000 pages (planning on way more
Permalink structure: /%category%/%postname%
Hardware: Very powerful virtual machine; 4 CPUs with 2,5Ghz each, 4GB ram, 15000RPM disks etc.
Thanks for any input.