Free RAM plummets when rMBP is pugged in.

Discussion in 'MacBook Pro' started by Collider, May 19, 2014.

  1. Collider macrumors regular

    Oct 8, 2009
    I've been noticing some very strange RAM readings from my 2012 rMBP (8GB). In both Memory Clean and Activity Monitor, it's consistently showing as little as 7MB free, while the 'used' section includes up to 3.5GB of 'inactive'/'file cache'. The odd thing is, this seems to only happen when the MBP is plugged in, and it does not come with any noticeable slowdown or lag. I spent the last couple of days running on battery, and it almost never dropped below 5GB free, which is much closer to what I was used to, and the performance remained exactly the same in both cases.

    I'm not too worried, because there's no noticeable slowdown, but at the same time I can't help think it's not healthy to be running on what claims to be less than 10MB free out of 8GB. So, in the hope that someone else on here might have had a similar experience, or know why so much RAM is being assigned to the file cache only when the machine is plugged in, I thought I'd ask around. Any thoughts / suggestions / explanations?
  2. chrfr macrumors 604

    Jul 11, 2009
    I don't know why it would be correlated with being plugged in, but you want all that RAM being used as a cache. If a program needs it, the memory will be released for that application. There's no reason to be concerned with this.
  3. simonsi macrumors 601


    Jan 3, 2014
    This is OK and normal.
  4. thundersteele macrumors 68030

    Oct 19, 2011
    I'm guessing a bit here, but maybe this is part of the energy optimisation.

    The one thing I find strange though is that I had the impression that it works the other way round: RAM is used up on battery, and freed up when plugged in. However this observation was based on comparing iMac and rMBP performance... I will keep an eye on my RAM usage with/without power.

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