"Inactive Memory" ??? please explain

Discussion in 'macOS' started by mikey12784, Oct 27, 2005.

  1. mikey12784 macrumors newbie

    Joined:
    Oct 18, 2005
    #1
    i have teh new 1.33Ghz 512 ram 12.1 inch ibook, and i like it alot, but what the heck is inactive memory, its taking anywhere form 20 to sometimes like 200 megs of my memory, that could really be used for other things... like world of warcraft, im going to get another 512 megs @ some point, but i dont want to do that quite yet. If there is a way to get rid of/reduce this, id love to know! (or at least know what it does/is) thanks guys, Mike.
     
  2. mjstew33 macrumors 601

    mjstew33

    Joined:
    May 29, 2005
    Location:
    Illinois
    #2
    My guess is, but I'm not positive, it's simply memory that can be used by other apps.

    Correct me if I'm wrong :eek:

    Oh, and this thread would be better off in the Mac Help category. Your a noobie... we all learn :D
     
  3. jsw Moderator emeritus

    jsw

    Joined:
    Mar 16, 2004
    Location:
    Andover, MA
    #3
    Memory types:
    • Free: This is memory available for use immediately by an application or the system.
    • Inactive: This is memory that has been used, and could be used again if needed. Swappable.
    • Active: This is memory currently in use. Swappable.
    • Wired: This is memory currently in use. Not swappable.

    Basically, if you open and then close an app, file, etc., OS X keeps it in memory as long as possible in case you open it again. If some other app needs the RAM, OS X gives it away. That's what inactive memory is.
     
  4. mikey12784 thread starter macrumors newbie

    Joined:
    Oct 18, 2005
    #4
    aha, looks like i really do need some more mem, o well, had to happen eventually i guess, must have REALLY sucked for people who had tiger and the old ibooks with only 256 megs to start, that had to be painful. im kinda surprised tho, it doesn't seem very memory efficient, my windows PC is @ less than 95 megs of ram used @ startup, and after runnign stuff for 2 days and exiting all running programs, its only @ like 180-200, and this guy stays @ like 500 used after using stuff, until i restart it. but hey, like i said i really like this machine, so if i need 512 more to make it real nice, 512 more it will get :)
     
  5. jsw Moderator emeritus

    jsw

    Joined:
    Mar 16, 2004
    Location:
    Andover, MA
    #5
    Not sure why you think you need more RAM... as you use OS X, inactive memory fills up as you use then close apps, resources, etc. It's the SAME as free memory except that, if you restart that app or reuse that resource, it'll start/load vastly quicker. If you have 16GB of RAM, you can fill it with inactive memory. This is a GOOD thing, not a bad thing. Just an optimization.
     
  6. OutThere macrumors 603

    OutThere

    Joined:
    Dec 19, 2002
    Location:
    NYC
    #6
    You're fine...on a PC the used statistic is referring to the "Wired" memory, which is stuff that cannot be swapped out. Here's a pic of my activity monitor breakdown right now, with just Firefox and iTunes open (my computer has been on for 9 days):

    [​IMG]

    It says 419 mb used...this is referring to all of the memory that has something in it, whether or not it can be quickly replaced with something else. In fact, I've only got 76 mb of memory that can't immediately be replaced with something else if need be. I almost never hit the point where my memory is maxed out...and if I do the processor and hard drive are usually overwhelmed before the memory maxes out. Now, on my video editing machines I wouldn't pretend to play with anything less than 1gb...but for any normal use of the computer, 500+ is perfectly reasonable. :)
     
  7. mikey12784 thread starter macrumors newbie

    Joined:
    Oct 18, 2005
    #7
    ahh, well thats not too bad, working on finishing installing WoW so we'll see how that runs, not expecting much, but i normally run it with 2 gigs on my main machine lol. guess we'll find out.
     
  8. OutThere macrumors 603

    OutThere

    Joined:
    Dec 19, 2002
    Location:
    NYC
    #8
    It'll be decent...but the bottleneck is in the graphics memory, not the main memory. 32mb will work for most places/raids up through 15 people, but in MC/BWL/ZG the frame rates will bottom out to near-unplayable. :(
     
  9. mikey12784 thread starter macrumors newbie

    Joined:
    Oct 18, 2005
    #9
    to be expected, its not replacing my machine tho, its just for when i go home or something like that its nice to have something to play wow on still
     
  10. ElectricSheep macrumors 6502

    ElectricSheep

    Joined:
    Feb 18, 2004
    Location:
    Wilmington, DE
    #10
    Well, there are really two kinds of inactive memory: dirty and clean. The difference is if the page has been written out to the backing store.

    If a page which has been moved to the inactive list has been modified, but has not been written out to disk, it is referred to as dirty, and it must be paged out before it can be released.

    If the page has not been modified (hence the copy in the backing store is still valid), it is clean and can be stolen into the free memory list right away.

    All in all, you can either think of it as an 'optimization' or you can think of it as lazy memory management. Its an optimization in the sense that you get the benefit of having 'soft' page faults (moving pages from the inactive list to the active list) over 'hard' faults (paging memory in from the backing store on disk). Its lazy memory management in the sense that you don't need to spend the effort releasing inactive memory until you actually need that space in physical RAM. You put it off until its really necessary.
     
  11. generik macrumors 601

    generik

    Joined:
    Aug 5, 2005
    Location:
    Minitrue
    #11
    Inactive memory sounds awfully like a disk cache..
     

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