I know there are tons of performance requests out there, but I really can't find the reason for this:
I have a dedicated server
I have APC running well - no frags, etc
I have xhprof and devel
I don't have too many modules (about 20 contribs)
I have caching of all types
Typical devel results are:
Executed 87 queries in 17.58 milliseconds. Queries taking longer than 5 ms and queries executed more than once, are highlighted. Page execution time was 140.99 ms.
Memory used at: devel_init()=2.44 MB, devel_shutdown()=10.94 MB.
Intermittently, a page will serve at +- 130 ms, but will go back to around 1200 - 1500 ms on an irregular basis i.e. sometimes they are fast, and sometimes slow.
xhprof always reports the same thing. All the functions are quick, but main() varies. When main() is quick, the page load is quick. When main takes a second (Excl.), the page load takes just over a second.
main() is not a function so xhprof can't really help me further.
I tried to use tracing. The kicker is that a page is NEVER slow when tracing is applied to it - in other words, tracing prevents whatever the delay is 100% of the time, which prevents me from finding out what it is.
I'd like to know if anyone has ideas to help me isolate what is happening?
Any help would be super appreciated.