: How to start troubleshooting extremely high ttfb on large queried pages? We have a dedicated server that feeds a very large wordpress site with a lot of advanced queries - large integrated CMS/Video-enabled

We have a dedicated server that feeds a very large wordpress site with a lot of advanced queries - large integrated CMS/Video-enabled with a ton of extra WP fields added on.

The server is 32G memory, 4Quad running W2012 with apache(2.4)/php5.6.3/mysql5.7/tomcat8 - everything over ssl.

The server stack was just recently updated and we haven't finished configuring it.

With just some basic tweaks... things aren't running to great.

A static page is at 240 ms - great.
a wordpress page out of the box with no plugins... 800ms-1.2s... not great at all.
Our main site - just a blank page. About 800ms... blah.
Our main site homepage - about 2-4 seconds
Our main site page with a lot of dynamic queries - 4-30 seconds (kid you not).

Background: Before the server was upgraded to the latest stack our sites performance was much quicker but we were getting a ton of out of memory errors - and these happened at a greater rate on larger pages but always around random code bits. Since the upgrade we have had zero memory errors and really no php errors at all.

I can copy over server configurations if needed but I have php's memory set at 2GB, I have 15G allocated to innodb, and I have played around with the mpm worker settings - and really everything I do, doesn't really effect the server ttfb issue. No errors in apache logs, nothing in php logs.

I am noticing extremely high CPU utilization by apache - we are only getting like 10K hits a day and it is always back and forth between 50-95% staying closer to 80% most of the time. Also I notice that the CPU pegging happens instantly after I restart apache with no visitors. At the same time apache appears to be using very little memory - 300M max when before our upgrade apache was always at 1G plus.

(Side question here - is there a utility to see what apache mods are using CPU/memory - ON WINDOWS)

Where is the first place I should start troubleshooting this? I would like to keep the WP side of this out of the question - that can be its own question. For instance on our heavy pages I mentioned 4-30 seconds... 4 would be acceptable for now. I am wondering why we are getting the ttfb extreme spikes. Let me know what other info you need me to provide. (also can someone add W2012 tag?_