There seems to be a problem in Magento's reading of the var/cache directory. I've disabled Full Page Caching for testing.
When I execute the bash command chmod -R 777var/cache/` before loading the page, it loads ~3 seconds quicker (the time it takes before 'mage::dispatch::routers_match' is reached in the Profiler is reduced from ~4 seconds to ~1 second).
This speed-up remains a while but then is lost until the chmod is called again.
I'm guessing this has to do with writing permissions somehow? The odd thing is, the cache contents are afaik owned by the process that is executing magento (the web user).
Does anyone have any clues what could be the problem or what could be changed to prevent this?
(Magento version: 1.12.0.2)
UPDATE
It seems that not all cache files are created for the same user, but are created for two different users. Will have to inspect how that is possible..
I found the solution. I called my cron job internally from a different user than the web user, so all cache created via the cron job functionality was created for a different user. Problem is solved now I call the cache with wget from url. Thanks.