Question about Mavericks memory compression

Discussion in 'OS X Mavericks (10.9)' started by rye9, Oct 24, 2013.

  1. rye9 macrumors 65816

    rye9

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    New York (not NYC)
    #1
    Can anyone explain this to me in a way that addresses what I'm experiencing? (As follows...)

    So, I am under the impression that "swap used" is when you use your HD as 'RAM' when you run out of actual RAM. Please stop me here if this is wrong.

    If that is true though, then I'm a bit confused, because on my Mac with 4GB RAM, using Mavericks, I have no swap used but I periodically check my available HD space, and it progressively decreases. I haven't been downloading anything, so I am near 100% certain it's coming from using it as memory. I am a bit concerned if this actually is true, because I would have hoped and expected that the revolutionary new memory management with the OS would prevent this from happening, whereas on all previous OSs on my mac, I've very rarely had memory written to the HD (I would monitor my RAM and close programs when needed to prevent the 'page outs' and 'swap' from occurring).

    Any insight would be great, thank you! :)
     
  2. Quackers macrumors 6502a

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    #2
    Have a look at Activity Monitor > Memory tab
    The bottom left entry shows swap used. Ideally it should show Swap Used 0 bytes
     
  3. rye9 thread starter macrumors 65816

    rye9

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    #3
    Yes I understand that... but my question is, if my swap is reportedly zero bytes, but I'm seeing a reduction in HD space... I'm assuming it's due to memory being used on the HDD. I guess one crucial question I have then, is what's the difference between page outs and swap used? I don't see "page outs" anymore... but the behavior I'm seeing now is indicative of page outs, which I guess I was hoping would be a thing of the past with the 'improved' memory management.
     
  4. Quackers macrumors 6502a

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    #4
    If swap is not being used your HDD space reduction is being caused by something else, which seems more likely in any event.
     
  5. rye9 thread starter macrumors 65816

    rye9

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    #5
    Any ideas what's eating at my HD then if I'm not downloading anything? Through scrolling sites in Safari and through a PDF in Preview, I get the occasional blip of the rainbow wheel... I'm not saying I don't believe you but it really seems to me I'm getting "page outs" at the very least, not necessarily 'swap' I guess. In which case I'm very upset I upgraded to Mavericks... my machine is lagging whereas I never experienced issues (the rainbow wheel) in Preview or Safari.
     
  6. Quackers macrumors 6502a

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    #6
    I don't know what to suggest regarding your HDD issue.
    However, regarding the rainbow wheel, I've been seeing it appear randomly (and an all blue one too). Sometimes I'm not doing anything or even clicking on anything when it appears.
    It's only very briefly and has no impact on performance though it did immediately after upgrading to Mavericks.
    My system runs fine now, very well in fact but I do still see the odd pinwheel.
    I have no idea what's causing that.
     
  7. Weaselboy Moderator

    Weaselboy

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    #7
    Do you have Time Machine turned on? If you do, it saves data to local backups and that will use some space. You can ignore it though, as OS X manages the space and will free it up if you need it.
     
  8. MrGimper macrumors 601

    MrGimper

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    #8
    It could also be the system creating and using temporary files.
     
  9. rye9 thread starter macrumors 65816

    rye9

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    #9
    Nah I've got that turned off. I guess it could be the "temporary files" as the last poster suggested. It's just odd though because this slow reduction of free space did not happen with previous OSs. Of course I may just not have noticed it, but I was (and still am) pretty anal about monitoring free space and RAM. I still, unfortunately, am in severe disbelief of Mavericks handling the RAM better on my machine in particular, because all signs seem to point that I'm getting page outs when just letting my system sit. Is there a way to even see page outs in the system, now? That of course would solve a lot of this mystery since that's what I expect is happening
     
  10. Weaselboy Moderator

    Weaselboy

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    #10
    If you go to the memory tab in Activity Monitor and look at the lower left there is a readout for "Swap Used:"... that is what page outs was before. So if you have swap space used that means memory is full and data is being moved off to swap files on the drive.

    Do you have swap space used with a idling machine and not much running? Maybe try a reboot then use the machine normally for a couple hours and see what swap space used says.
     
  11. rye9 thread starter macrumors 65816

    rye9

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    #11
    Is this proven? Both "page outs" and "swap used" were their own respective categories in the previous Activity Monitor.

    And no, I haven't seen any swap used before and after a reboot with a few hours usage.
     
  12. Weaselboy Moderator

    Weaselboy

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    #12
    They are a different way of expressing the same thing. Pageouts before was cumulative, where swap used is not and shows what is currently in use as swap.

    There is a good write on all this here.

    If you have no swap used after a few hours of normal usage, you are not memory constrained.
     

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