installing APC php caching for multiple sites

[psygarden]

Could some please explain me what the ideal setup would be to activate apc caching for websites hosted using this platform?

i have 128mb of shm_max memory alocated, that i want to distribute over all sites that are active on my website, if possible dynamically/globally (though it's been pointed out that this isn't recommended)

what setups do you use for this kind of caching?

greetings,
Rik