For those poor souls who are developing with Magento but are not running linux with no access to kcachegrind, here is a diagram of what a simple request to the front page of Magento looks like.
The left side of the graph shows the “app” init sequence.
The right side shows the front controller being loaded (from “app"). Then the action spiders down some preDispatch functions, and finally calls the chosen controller’s “indexAction”. This is what happens when you don’t have a POST (i believe). From there the indexAction splits off into some template blocks and template layout legs.
Hope it helps.
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