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Is it time to buy more RAM?

iShater

iShater

macrumors 604
Aug 13, 2002
7,026
470
Chicagoland
To check how much VM files are being created, open Terminal

Type:

ls -al /var/vm

that will list with details the files in the /var/vm directory.

OSX will delete those files when they are no longer needed, so you don't have to reboot. I am not sure on when exactly they get used/removed, but the moment the system is out of memory it will create the swap files, to make room in RAM. I doubt they are all in use at the same time though.
 
IJ Reilly

IJ Reilly

macrumors P6
Jul 16, 2002
17,909
1,496
Palookaville
iShater said:
OSX will delete those files when they are no longer needed, so you don't have to reboot. I am not sure on when exactly they get used/removed, but the moment the system is out of memory it will create the swap files, to make room in RAM. I doubt they are all in use at the same time though.
Click to expand...

They don't though. Some will be deleted on a log out, but not all. To get back to the base state, rebooting is required. Check it out.
 
CanadaRAM

CanadaRAM

macrumors G5
Oct 11, 2004
12,417
6
On the Left Coast - Victoria BC Canada
IJ Reilly said:
As above, I don't think page in/page out ratios are very meaningful. What you really need to know is how much the OS is borrowing from your hard drive. At the moment Activity Monitor shows a page in/out ratio on my Mac of 2:1, but since the system has created no extra VM swap files, this supposedly "high" ratio is of no real consequence.
Click to expand...

Well its not the number or size of the swap files that is important, its how often the OS has to stop and read/write from the hard disk when it doesn't have the necessary information in RAM or enough RAM to do the next operations.

That's why Page Out/In ratio is promoted as a measure of the impact of VM swapping, there's little or no penalty to a Page In, but there is a speed penalty to a Page Out. The Page Out happens when the OS finds there is not enough physical memory and it has to clear out a page of RAM and send it to the disk.

Because the absolute numbers (ins, outs or swap files) are variable with the length of time the machine has been booted, the numbers themselves aren't a good measure, but the ratio is a more reliable indication of how often the machine has had to pause to make memory room. (It's also easier to monitor than the number and size of swap files on the disk)

Apple Virtual memory developer page

http://www.thexlab.com/faqs/lackofram.html
 
IJ Reilly

IJ Reilly

macrumors P6
Jul 16, 2002
17,909
1,496
Palookaville
CanadaRAM said:
Well its not the number or size of the swap files that is important, its how often the OS has to stop and read/write from the hard disk when it doesn't have the necessary information in RAM or enough RAM to do the next operations.

That's why Page Out/In ratio is promoted as a measure of the impact of VM swapping, there's little or no penalty to a Page In, but there is a speed penalty to a Page Out. The Page Out happens when the OS finds there is not enough physical memory and it has to clear out a page of RAM and send it to the disk.

Because the absolute numbers (ins, outs or swap files) are variable with the length of time the machine has been booted, the numbers themselves aren't a good measure, but the ratio is a more reliable indication of how often the machine has had to pause to make memory room. (It's also easier to monitor than the number and size of swap files on the disk)

Apple Virtual memory developer page

http://www.thexlab.com/faqs/lackofram.html
Click to expand...

The technical document don't help me, and don't think they'd help many of us. Checking VM swap files is a cinch, and I have found in years of doing it that this an easy and highly reliable way of determining when RAM has come up short. It may not be technical, but it works. ;)
 
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