OS X Virtual Memory

Well, I thought I might post this in a thread of its own. I am still discovering OS X as you guys may know by now. After being puzzled like some other people by the space used by the OS, I found out that OS X's VM has a very enthusiastic approach, to say the least.

here is a shot of the size used by the VM after a while. I was running Safari, Preview, and a few other tasks, like Virtue Desktops,Menu Meters and QuickSilver - nothing too fancy. Well, OS X decided to allocate almost 12GB of virtual memory!
Upon closer inspection, I see that most threads would get about 100x its size in RAM of virtual memory allocated.
Question is, is that normal? I know OS X has a somewhat different strategy for swapfiles, but this seems too much for me. Curiously, looking in the Terminal at /private/var/vm, where the swapfiles resides, gave a much lower number:

Code:

ls -lh /private/var/vm/
total 2097152
drwx--x--x   14 root  wheel       476B Jul 30 03:15 app_profile
-rw------T    1 root  wheel       512M Jul 23 01:47 sleepimage
-rw------T    1 root  wheel        64M Aug  9 23:15 swapfile0
-rw------T    1 root  wheel        64M Aug  9 23:27 swapfile1
-rw------T    1 root  wheel       128M Aug  9 23:28 swapfile2
-rw------T    1 root  wheel       256M Aug  9 23:31 swapfile3

Can someone explai what's going on? Also, do your Macbooks/MBPs also allocate this much swap?

 

Well first question is, are you noticing a slowdown or something?

If not don't complain and follow the saying "If it isn't broken, don't fix it!"

 

No, no slowdown so far, but I like to understand how things work. And I'd like to know how much can I fill my HD - must I always spare 12GB for swap? It doesn't seem reasonable.

 

I just went in and chcked mine and my swapfile is 13GB.

I think it's just setup that way, so if you fill up your ram it starts using that.

I have 2GB of ram and have 1.23GB of memory free right now, now if I fill that up, it would start using the VM. I think its on-the-fly VM as well, meaning that is continually adjusts.

According to my terminal, I'm only using 64M swap file right now, but I doubt it's being used.

 

Thanks, at least this means my Macbook is not going nuts.

We can draw three conclusions:

1- A large part of the "missing HD space" is going into swapfiles (assuming Activity Monitor is reporting the real thing). That means OS X itself doesn't take that much space, and *if* there are no problems once there is less than 10-12GB left on disk, everything is fine.
2- The amount of swap (pre)allocated seems quite independent from the physical amount of RAM available, since I have 512MB and you have even more swap than I do, albeit with 2GB (which is the maximum amount of RAM the Macbook supports incidentally).
3- Either Activity Monitor isn't reporting the real space used (in case my conclusions one and two above are moot) or not all swapfiles are located in /private/var/vm.

Googling didn't show anything conclusive - other than a statement that the VM can indeed grow so big. I'll look at Apple forums and maybe post there.

 

wow, my ibooks VM is only about 4 gigs.

i believe that the activity monitor reports how much is reserved, not necessarily how much is being used at that moment.