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I bought a Macbook Pro 15 inches 3 months ago. It's running on Mac OS X Snow Leopard and it has 4GB of RAM.

I consider having a fair use of this computer :
- surfing (Chrome)
- developing (Fraise)
- gaming

But after some hours of use, here is what happens :

enter image description here

It's in french but you can easily see that only some tens of MB (Mo) are still available, whereas the sum of all launched processes is far to reach 4GB...

So where the hell did my RAM go ?

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4  
You need to show the other other users' processes as well –  Mark Sep 20 '11 at 12:47
5  
There's more memory available than you think, because the 1GB of "Inactive" memory is available to be used -- it's holding old information that's not needed any more, but it's kept in memory as long as there's any free memory so that it can be used again if it's needed again. –  Mike Scott Sep 20 '11 at 13:26
    
Ok, thanks for the info. Mark, you should have post your comment as a answer ! –  Pierre Espenan Sep 20 '11 at 13:34
    
But that is not necessarily the answer - show what all processes show then we can provide more information on what is happening –  Mark Sep 20 '11 at 15:36

3 Answers 3

up vote 8 down vote accepted

There's more memory available there than you think. "Inactive" memory is memory that has been used, and is essentially keeping its old data so that it can be swiftly grabbed again if needs be. However, if your computer needs the memory for some new process, that memory is capable of being used - the old data is dropped out, and new data is put in.

As others have said, you also need to show all processes for a full idea of what's going on with your memory. But you're not nearly as tapped out as it first appears.

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You are displaying only your processes 'Mes opérations'. You can switch to 'All processes' to see what is using the remaining part of the memory.

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Unix-like kernels automatically take almost all available memory for the page cache. The page cache is essentially a copy of portions of your hard drive present on DRAM. This greatly improves performance. As your applications require more memory, the kernel will quickly decrease the size of the page cache to give the applications more room.

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