Memory All Used: Parallels or MacOS X issue?

I have a MacBook Pro with 2GB of RAM. If I start up a single VM with Windows XP SP2 and allocate it 256MB of RAM, eventually watching activity monitor shows that all but about 30MB of my RAM is used up, mostly in "Inactive".

Is this perfectly normal, a Parallels issue, or a MacOS X issue?

I upgraded to 2GB from 1GB of memory because it seemed that with 1GB when memory was getting tight MacOS X applications started just quitting like crazy.... Safari, Mail, etc. just crash and burn when memory was getting tight and Parallels was running.

Referenced below is a screenshot of my Activity Viewer window after having let Parallels run for about five minutes with no other MacOS X apps running (except background tasks like QuickSilver/etc). It's too big to attach, so I linked it.



Thanks!

 

I guess that it's perfectly normal. It doesn't seem that Parallels uses more memory that it's allowed to.

 

Yeah, it's normal for OS X to "use" all of your memory. It devotes to caching what isn't claimed by applications.

 

Fair enough, but I've just never seen it get that full until I ran Parallel's workstation, and I've been using Mac OS X since the public preview. I've seen it use a LOT of memory, including some for caching, but not right up to the limit leaving almost none free. I'll just keep an eye on it.

Update: Read this note over at Apple, helps clear up the terminology of the various segments.

http://docs.info.apple.com/article.html?artnum=107918

However, Parallels is still running with REAL memory of what I'd expect (384MB allocated to VM, Real Memory use of 396MB), but why has it allocated 553MB of Shared Memory? Is that "real" physical memory, or does that include pages cached out into Inactive but not freed yet?

 

The thing to look for is your page ins/outs values, specifically the outs value. If your memory is really full you'll see loads of page outs, because the computer is needed to use the Hard Drive as active Virtual memory.

Your value of "1481" is extremely low, suggesting that you have no problems with running out of memory.

You're fine!

 

I guess inactive memory is used for various caches - for caching virtual disk for example...

 

Basically, OS X like Linux and Unix are designed to use all available ram - this is a good thing (TM).

The buffer cache is designed to grow and utilize all available ram, but it'll also 'give back' memory just as effectively. As in, if you're just running a free basic applications and you don't have much memory 'free', the moment you open Photoshop the kernel will resize it's buffer cache, free up memory and allocate what's needed to Photoshop to function faster.

The exception of course is when you don't have enough memory to start with, which is when you'll see page in/outs start to go up and you'll see a performance hit.

But really, Mac OS X is designed and it's a good thing for it to be using most, if not all, your memory at times - It has a much, much difference memory management that over Windows which won't make the most of all your memory at every given time.