Home / server / Questions / 356556
In Process
Greatestswordsman
Asked: 2012-02-04 06:49:22 +0800 CST

APC keeps flushing

  • 772

See my APC here: http://www.animefushigi.com/apc.php

If you keep hitting the Refresh button on the top left, watch the number of "Hits" and the "Start Time" and "Uptime" values. They all go up and down.

I find this quite strange, normally all 3 of these values should only get higher as time passes, not go down (except Start Time - which should stay the same)

My only assumption is that the cache is being flushed every second.

I've searched around and have tried a few things to fix this

  • disabled suEXEC
  • set apc.mmap_file_mask /dev/zero
  • tried PHP 5 Handler fcgi and cgi

also when I go to /tmp/ on ssh and do -ls I don't see anything apc related.

Any suggestions ?

The server is linux and uses whm/cpanel

*edit: I have a suspicion that the problem may be due to apc.mmap_file_mask. Currently it's set to /tmp/apc-animefus.XXXXXX but on the apc.php page it seems the xxxxxx is replaced on every refresh to something else

php apache-2.2 alternative-php-cache opcode

1 Answers

  1. Some notes about APC and the different modes:

    • APC's cache is essentially per-process.
    • If you use CGI, the process is created, APC creates its cache, and then the process ends and the cache clears. (from what I can find, suPHP seems to be CGI-like).
    • If you use FastCGI, Apache spawns one process for each simultaneous request. It keeps them around in case they'll be used again. Each process has its own APC cache.
    • If you use the mod_php handler, it shares the cache among all the apache processes, but doesn't run it as the user.

    Observations:

    • The cache is not resetting on every page refresh, I am seeing several that are being reused that are now five minutes old. Any reconfiguring of the server would've reset this.
    • The only way to know you get the same FastCGI process is to be the only client.
    • There may be so many requests on your website, that there are several FastCGI processes in use.

    Things that should be true:

    • While in CGI or SUPHP mode, the values never go up.
    • While in fcgid mode, the values go up and down.
    • While in mod_php/DSO mode, the values are correct.

    Things I'd check (not in any particular order):

    • Watch PHP processes under your user (using top or similar). See how long they typically run and if they exit.
    • Check Log files to see how many requests is hitting PHP.
    • Create a script to check the process ID that the script is run as, if you like write them to a database/file so you can keep track of them easily. Keep loading this page to gather information about how long the process runs.
    • Check FastCGI configuration, I'm not sure how cPanel configures it by default because it always had a few issues with some websites when I tried it. There are several options that control how long a process should stay alive. PHP, by default, will exit after 500 requests in FastCGI mode. This is purposeful as some have reported PHP leaking memory after running for a very long time. If your site gets a lot of hits, you may want to bump this number up.
    • 2