How can I tell if I need more RAM?

Discussion in 'MacBook Pro' started by doxavita, May 28, 2011.

  1. doxavita macrumors 6502a

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    Jul 6, 2010
    #1
    So if I run all the processes I need and have them loaded for a while, how can I tell if my RAM usage is fine, if it's running short, and if I simply need to buy more? (I recall it involved going into the Activity Monitor and looking at the system memory tab...
     
  2. Matthew Yohe macrumors 68020

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    Oct 12, 2006
    #2
    If your page outs or swap used is large, then you might need to consider more RAM. A screenshot of your activity monitor would be helpful.
     
  3. doxavita thread starter macrumors 6502a

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    #3
    Really? So it has more to do with page outs and swap than the "Free" (in green) amount?
     
  4. Matthew Yohe macrumors 68020

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    Oct 12, 2006
    #4
    Yes, because note the blue "inactive"... That can be easily reclaimed if something needs more RAM.
     
  5. alust2013 macrumors 601

    alust2013

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    #5
    Yes and no. The ratio of page outs to page ins shouldn't really exceed 1:10 or so, but if you notice a significant amount of page outs regardless of page ins, it may be a good idea to get more RAM. As far as free memory, if that's often less than 250MB or so, it would also be a good idea to get more. You would generally see those things coincide.
     
  6. doxavita thread starter macrumors 6502a

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    #6
    Right, I often see the Free amount below 250MB when running my Windows 7 VM through Parallels, however, the Page outs and swap are nowhere near that ratio..
     
  7. Matthew Yohe macrumors 68020

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    Oct 12, 2006
    #7
    If you're running a VM on top of OSX, then you likely could greatly benefit from more RAM, just by the fact that you can dedicate more to your VM, and give more room to your host.
     
  8. talmy macrumors 601

    talmy

    Joined:
    Oct 26, 2009
    Location:
    Oregon
    #8
    "Free Memory" is going totally unused, so is essentially a waste. You are actually using the "Wired" plus the "Active" totals. The "Inactive" is loaded up but isn't currently being used. You need more memory when Free+Inactive approaches zero.

    However the Ratio between Page Ins and Page Outs is most important as that tells you if you have been swapping. But even then that has to be tempered against run-time.

    For instance the first attached image shows the usage on my server which has 4GB of RAM. Virtually no space is free, yet less than 3GB is actually being used, and it's pretty steady. Paging ratio is about 3:1 which looks bad, but the system has been running for 20.5 days. It takes about 8 seconds to swap in that 778 MB, and I feel that loosing less than half a second per day for "not having enough memory" is fair enough. The server runs a Windows VM all the time, as well as a number of server programs.

    The second attached image is from my iMac which has 8GB of RAM. It has been running for 11 days. Current usage shows that I probably would be all right with 4GB of RAM, and certainly 8GB has been more than enough since it essentially has never needed to page out. When I took the snapshot, it was not running a VM, but I configured it with 8GB so it could easily run one running a CAD program which takes 1GB by itself.
     

    Attached Files:

  9. doxavita thread starter macrumors 6502a

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    Jul 6, 2010
    #9
    Great post, thx! :)

    I did not know all that. I was thinking of disabling Windows Update in my Windows 7 VM thinking if the RAM got too low the system might not update properly when trying to shut down the VM thus damaging the system?! But now I know that "Free" is not that important, so I'll have a closer look next time I boot that VM (with the ratios). So I can leave my VM running for as long as needed? (4GB of RAM in my MBP), wouldn't want to go through a crash....
     
  10. Matthew Yohe macrumors 68020

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    Oct 12, 2006
    #10
    Your VM isn't going to crash. You set the RAM when the VM starts, and it eats up that entire amount right when the OS is starting up, so your host (OSX) won't be able to even touch that RAM allocated to your windows machine.
     

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