Yup, you found it. OS-X does use virtual memory via the hard drive.
When you start up it looks at how much physical RAM you have, how much
free hard drive space you have available and then through some arcane
formula previously known only to alchemists decides on how much hard
drive to set aside as virtual memory.
I know you hate the Terminal, but humor me this once... (smile)
open Terminal and type the command:
top
then hit return
toward the top of the page get back you might see something like:
MemRegions: num = 3220, resident = 60.7M + 9.20M private, 76.5M shared
PhysMem: 43.0M wired, 92.8M active, 177M inactive, 313M used, 303M
free
VM: 2.61G + 63.9M 9907(0) pageins, 0(0) pageouts
This is the virtual memory amount that has been set aside. if for some
reason, drive space is low, OS-X gets very cranky. (I guess the
alchemists didn't think about how cranky a machine can get, sicne this
was also the dawning of logical positivism).
Side note: If you see the pageouts number getting big, that means your
system is, well, under stress as it is saving memory segments out to
the drive (another reason why you want to use the shutdown option
rather than turning the machine off !!)
Jerry
On Sunday, December 22, 2002, at 12:17 AM, Dan Crutcher wrote:
> I'm still trying to figure out my recent problems with X (which were
> cured eventually by a reinstall) and I may have found a clue. I again
> experienced some of the same symptoms, though not nearly so bad this
> time. And it happened in a situation very similar to the one a few
> days ago.
>
> There are at least two factors that were the same on both occasions: I
> had booted into OS 9 and I had performed an operation that created
> large files that nearly filled up my hard drive. When I tried to boot
> back into X (this time 2.1.3), I found that my desktop was unstable.
> The icons and the date and time on the right side of the menu bar were
> flashing on and off; my desktop icons had resized themselves to the
> default size (I had set them at 32x32) and the dock had returned to
> its default size and it was no longer hidden.
>
> Before the operation that nearly filled up my hard drive
> (postscripting some Quark pages that had large graphic links), I had
> about 1.0 GB of free space (on an 18.6 GB drive). After creating the
> new files I had about 135 MB of space left. This was the case each
> time that I encountered the problem.
>
> This time my system seemed to work more or less normally with the
> exception of the weird desktop stuff mentioned above, so I immediately
> deleted about 500 MB worth of files -- and immediately after doing so,
> my date, time and menu bar icons reappeared and no longer flashed on
> and off. I reset my icons and dock to their previous settings and
> restarted, and everything seems to be working fine now.
>
> It appears that, on my system at least, OS X gets real cranky when I
> don't leave it plenty of hard drive space to play with. Any idea why
> that might be the case? X doesn't have a virtual memory setting like
> previous versions did, but I'm wondering if it doesn't reserve some
> hard drive space for use as virtual memory. I have 512 MB of RAM, if
> that makes any difference.
>
> Any thoughts on this?
>
> Dan
>
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