memory

hello,
I'm upgrading my site and I have some question on memory.
I try to use Doctrine, models, and all this stuff.
By making some benchmark I noticed that a single request can take 4Mo of
memory.
Is that huge? Or is that acceptable in face of the beneficts of a good
architecture ?

I read that the default configuration allow 128Mo so 4Mo can seem
ridiculous, but I am not sure.

So if you can give me your feeling.

Thank you