A new take on the old "inactive memory" question.

Discussion in 'MacBook Pro' started by Sankersizzle, Oct 9, 2010.

  1. Sankersizzle macrumors 6502a

    Sankersizzle

    Joined:
    Jun 5, 2010
    Location:
    Canadadada
    #1
    Hello, ladies and gentlemen. First, I want to thank y'all for providing me with answers to questions I never asked through my lurking.

    But one of my questions remains unanswered, so I thought I'd post. I did a search and a few relevant threads came up, but not exactly dealing with what I need to (as they are a few years old and common SSD's aren't).

    Anyways, I've noticed something a bit peculiar. Whenever I leave my Mac on for a bit, the RAM just gets eaten up. I have no idea where it goes. I used to be a big Windows guy who kind of knows his stuff (I'm in computing in uni to boot), but I'm confused.

    Right now, I have 2.2GB free,735MB Wired, 727MB Active, ~250MB inactive and 1.66GB used (total),with just Safari and iTunes open. In a few days, that will become 250MB free, 750MB wired, 2GB active, and 1GB inactive, with the same applications. Activity Monitor reports no real change in the memory usage of the open programs, it seems free RAM becomes inactive RAM.

    I understand that this is the way it's meant to be -I think, but I'm concerned because when it starts swapping to my SSD (even with all that inactive RAM) I've heard that can shorten the lifespan of the drive. Is this normal? Any way to stop the swap? I'm not trying to be one of those folks who goes "OCD" about every last component, but people elsewhere seem pretty steadfast on the notion that Swap + SSD = new SSD.
     
  2. holmesf macrumors 6502a

    Joined:
    Sep 30, 2001
    #2
    To (maybe) answer your question, having a lot of inactive memory isn't going to cause an increase in swaps (and hence writes) to your SSD. The only thing that could cause memory to be "swapped" to your SSD is if the system runs out of usable physical memory, and Inactive memory is part of that category. In fact, the more Inactive memory the better. Inactive memory works as a disk cache and so it can speed up launching of applications and reading of files.

    What you should really be concerned about is the number of page in / page outs. This actually refers to the amount of memory that has been swapped back and forth between your SSD and RAM since system startup. If these number are high (in the gigabytes) you should probably install more RAM. It can also be a bit confusing though, because some swapping can be reported that is not related to RAM shortage (memory mapped i/o for example, I think!)

    see this tech note about the meaning of active versus inactive RAM: http://support.apple.com/kb/HT1342?viewlocale=en_US
     
  3. Chase R macrumors 65816

    Chase R

    Joined:
    May 8, 2008
    Location:
    PDX
    #3
    Safari and iTunes will chew through LOTS of RAM. Right now Safari is using over 600MB of RAM alone, and it hasn't even been running all day.

    iTunes isn't bad until you switch to a view that displays album art (CoverFlow or grid cause all those image files to be read into RAM), then it really starts chewing through RAM. I've seen my iTunes get as big as 1.4GB (I did this purposely though to see how big I could get it).

    kernal_task also gets larger with use. I think it starts at around 70MB or so but easily grows to over 300MB.

    This is just OS X caching things to make the OS more responsive. "Free" RAM is wasted space.

    EDIT: Right now Safari is using nearly a 1GB of memory. Now I'm beginning to question whether this is normal?
     
  4. toxic macrumors 68000

    Joined:
    Nov 9, 2008
    #4
    people worry way too much about the lifespan of SSDs. don't worry about it. it will last just as long as an HDD in normal use.

    anyways, 10.6 has some sort of memory leak. it more or less got fixed for me in 10.6.4, but I know it was never there in 10.5. I know there can be a performance hit because I suffered from it when using Aperture 3.
     
  5. holmesf macrumors 6502a

    Joined:
    Sep 30, 2001
    #5
    I agree ... basically just don't worry :)

    However, you can always reduce the any potential problems by getting more RAM. And sinced you coughed up the dough for an SSD, you can probably afford it :D
     
  6. Sankersizzle thread starter macrumors 6502a

    Sankersizzle

    Joined:
    Jun 5, 2010
    Location:
    Canadadada
    #6
    Haha, alright. Thanks for the replies guys. I knew I might have been paranoid, but I didn't want to chance it. Now I know. I'll definitely get an 8GB kit for Christmas, solve all these problems at once. Learn something new about OSX here everyday, refreshing after being with Windows for so long!

    If kernal_task is caching things to make the OS more responsive, does this mean my computer is actually getting more responsive with less ram? :p
     

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