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In windows xp it was obvious: if the memory used regularly exceeded the physical memory, it was time to put some more in

What's the deal with the mac?

I read this and am none the wiser

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migrated from Jan 17 '12 at 12:46

This question came from our site for system and network administrators.

Just for info, for each simultaneous user, allow 4gb of memory. I increased mine by this rule and have xperienced no issues since – adolf garlic Jan 5 '13 at 11:33

If you don't have enough RAM, your Page outs value in Activity Monitor » System Memory will be big and growing rapidly when you're doing memory intensive tasks.

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If you're experiencing poor performance and frequent disk accesses, it's time for more memory.

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+1 for explaining this in layman’s terms – kinokijuf Jan 17 '12 at 13:17
It's more poor performance with tasks that are usually quicker, isn't it? Everything else just means you're doing CPU bound processing. But once switching between applications is slow, then you have a RAM issue... – Daniel Beck Jan 17 '12 at 20:35
It's true that if switching between applications is slow, there is some amount of memory that would avoid that problem. But that amount can be much larger than your system could ever handle, and in that case, it's misleading to describe the cause as insufficient RAM. Rather it's simply that lots of information "passes through" the RAM and flushes anything cached across that operation. (Consider copying a 1TB folder from one drive to another. That will cause a task switch to be slow. But to say the issue is that you don't have 1TB of RAM is at least misleading.) – David Schwartz Jan 17 '12 at 20:40
I just meant to prevent the misunderstanding that just because something is slow doesn't mean you don't have enough RAM. It could also be the CPU. But those bottlenecks are much easier to determine. – Daniel Beck Jan 18 '12 at 17:26

When in Finder use the 'Go' menu, select 'Go to Folder...', type '/var/vm', then click 'Go'

That will take you to a folder showing you how many 'swap' files have been generated.

There is always one, and each new one is twice the size of the previous. The more swap files, the more disk thrashing.

More RAM memory will help prevent building swap files.

If I see more than 4 swap files and notice a slowdown changing applications, I will restart.

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