I have a LAMP stack with APC installed. I have a WordPress site on this server. Is WP taking advantage of the opcode caching? I have done no WP configurations. My understanding is that simply having APC installed means that all PHP code is being cached. If that is untrue, please point me to the direction where I can configure WP to take advantage of APC.
Note: I thought about this as a ServerFault question, but since the solution to is code related I posted on Stackoverflow.
Is WP taking advantage of the opcode caching?
Yes, it should be. You can install the apc.php script which will tell you exactly what pages are being cached.
Finding the apc.php script can be tricky.. You didn't mention exactly which distro you're using but this site has a decent example of finding and installing it:
http://www.debian-administration.org/articles/574
Edit: Direct link to apc.php in their repo: http://svn.php.net/viewvc/pecl/apc/branches/APC_4_0/apc.php?view=co