Misinformed much?
Inactive is NOT cache. It's recently used memory:
It is ALSO cache.
I don't care what you're pulling from an apple KB article (yes I've already read it), i can see it accumulating as I do disc accesses by copying files, etc.
And yes when RAM is full you WILL get page outs. However a modern OS with an efficient memory allocator (and this includes OS X, newer versions of Windows, Linux, other Unix) will swap things out that don't need to be in memory pro-actively to ensure there is more RAM available for cache, to speed up disk access for the apps that ARE running.
The app, once swapped out is likely kept in INACTIVE MEMORY as well, so that if it needs to be reclaimed, it doesn't need to be swapped back in from disk. However, if the memory is needed for something else, the inactive memory is re-allocated quickly, because the inactive app is
already swapped to disk - the OS doesn't need to wait for the swap to disk to happen before it can re-alloc.
The KB articles are sometimes very much a simplification for end users (and/or mis-interpreted), and are not necessarily fully representative of the way things work.
To answer the OP: your ram IS being utilised. the SWAP is the OS proactively swapping inactive things to disk so that if something else needs the memory it can be allocated. the INACTIVE memory likely contains the contents of what was swapped to disk, and the things in inactive memory will be kept there in case they need to be "swapped back in" before the inactive memory needs to be reclaimed for something else. If the INACTIVE memory containing the "swapped" pages was not reclaimed, no swap in needs to happen, the inactive memory just gets marked active again.
In short:
unless your mac actually has a performance problem, don't go trying to look for issues in activity monitor. Well, by all means, look.... just don't jump to conclusions that things are bad if you see numbers for swap, without taking it into the context of what else is going on.
Modern memory management is a LOT more complex than "free memory = anything I haven't loaded up with programs" and "swap = bad, i ran out of memory!". I'm sure the apple memory allocator probably also takes into account things i haven't listed above, such as whether or not the disk is an SSD, when it determines how aggressively it should try to proactively swap.
Yes, you can get an idea of how bad memory pressure is if a machine is being forced to use swap a lot (in that case, your "inactive memory" size will be small and you'll have a lot of swap), but just looking at swap and seeing a number there is no reason to freak out about your memory not being used properly...
In your case, with that much inactive memory, and only a tiny percentage of your system memory consumed in swap - you have nothing to worry about. If you had say, 8 gigs in swap, you'd have something to worry about.
Oh and one more thing: the purge utility is a debug tool, intended for debugging. Yes, it will give you a bigger "free" memory number in actvitity monitor - by dumping the inactive memory contents. Which will interfere with the above memory management process, probably slow down disk access, etc. No, it won't break anything, but it likely won't fix anything either. Other than making the free memory number bigger.
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