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I have a 27'' iMac (Late 2012, OS X 10.9.2) with 8GB RAM. The usage of memory is always above 7GB, even though I don't think I am running that much stuff. This leads to the occasional hanging of a program and occasional feeling of the computer being lagged.

The heaviest thing I am running is a Parallels virtualization of a defunct Windows laptop (for my Windows-only programs; work-related). Then I mostly surf with Chrome (10-20 tabs, some with youtube videos). Of course I have other things opened, like Mail, Evernote and a few more. But I don't think a 8GB RAM computer should be overwhelmed by that. I could be wrong.

I am willing to provide an export of processes from the Activity Monitor. I tried looking into it, of course, and I am running A LOT of small processes (unknown to me) -- system stuff I presume. I am a long-time PC user and I know my way around process management in PCs, but not on Mac.

What do you think? Do I just need more RAM or it doesn't feel like it?

Regards,

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What version of OS X? –  IconDaemon Apr 26 at 14:24
    
OS X 10.9.2. I edited the original post too –  Sonny Apr 26 at 14:41

5 Answers 5

up vote 10 down vote accepted

Because OSX manages memory (as does Windows) it is often difficult to tell if performance issues are caused by memory limits. Technically, you really want the OS to capture all the available memory and allocate as needed, in which case, you would see all of the memory being 'used', even though there may be memory available but not allocated by the OS.

This is somewhat analogous to what is happening in OSX and Win7+. However, Apple has made it confusing in the past with many memory classifications, like Wired, Swap, Real, etc.

Luckily, you are running Mavericks, and a new feature of Marvericks is the Memory Pressure graph, described in the Apple support document here: http://support.apple.com/kb/HT5890

enter image description here

Basically, if the memory graph shows Red, you need more RAM, if its Green, you are good. I suggest reading the article for more details, but the Red, Yellow, Green is a great visual tool to help guide where you might be seeing problems.

Depending on your model, I have personally found Macs suffer more from hard drive access speed than memory limits, so an SSD, if your iMac does not have one, has a huge impact (and unfortunately quite a bit of work to put into your iMac)

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As any modern operating system, OS X tries to make use of RAM as much as possible. For example, OS X:

  • keeps data in memory when an application quits to gain time if it’s launched again;
  • caches recently used files from your (slow, slow) hard drive for faster later access.

Obviously, this memory is still available for other uses if need be. But the system rightfully see no need to “free” it right now: it waits for the need to appear.

This means that, after running for a while, your computer will always indicate that your memory is completely used or almost. It doesn’t mean you don’t have enough RAM, just that the system doesn’t let it go to waste.

To know if you’re actually lacking in memory, you should mainly check if you’re swapping often. I would refer to @cmason’s excellent answer.

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Thanks for the edits. I also wonder if compressed memory was part of the culprit). –  Blaisorblade Apr 29 at 18:14

Get yourself an SSD. 10.9.2 knows quite well how to efficiently manage your RAM and you should not worry about it. As it is said above OSX will try and keep as much memory used as possible, for healthy reasons.

8GB is right for normal usage (heavy video/graphic editing not considered normal in this context).

I have an early 2011 15" MBP w/8GB that just became a different, way faster, machine when I installed an SSD. I run Win7 virtual machines off VirtualBox, with the virtual machines on an external FireWire 800 drive, no problem.

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I like @cmason's answer, but I'd like to clarify a few foundational things.

You have two separate questions here: (1) The lags you report is most likely hard disk-induced, as hinted by some answers. Going to the right place in a hard disk takes often on the order of ~10 ms, and these delays build up to be visible to a user. (2) Memory is full because the memory is used as cache of the disk.

The only relation is that when the system needs to read again the same stuff from disk, having more RAM used as cache could help (if what you need was kept in RAM).

But whenever the system reads new stuff from the hard disk, only a faster disk (an SSD) can help (alternatively, some systems try to guess what the system is going to read from the disk and read it in advance, but this cannot do miracles in general, since computers don't have crystal balls to predict the future).

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A RAM upgrade is cheap and easy so just do it rather than try to understand the complexities of memory management under OS X.

An SSD upgrade is expensive and hard (especially on an iMac) but will make a far more immediate and noticable difference. I’ve never tried it but I suspect that even running OS X off an external Thunderbolt-connected SSD would be faster than the internal spinning disk (although slower than an internal disk).

Most likely, between Parallels and Chrome, OS X ends up swapping memory to disk and disk i/o on a rotating disk is sloooooow. My experience is that browsers are reluctant to release memory over time so try restarting Chrome when you notice the problem. Most likely that’s easier than restarting Parallels.

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Re your first paragraph, this is exactly the sort of naive "solution" that the hardware manufacturers want you to use. "Just buy more RAM" No, don't! Understand what you're using and why. Don't let the capitalists win! –  Lightness Races in Orbit Apr 26 at 19:57

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