Whickwithy

Q: Where is the cache shown on the Activity Monitor stored?

On the memory tab of activity monitor, in the box at the bottom, there is a item called cache.  I am wondering where this is stored.  It is certainly not on disk, it is certainly not the cache that is part of the processor but, in some architectures, there is a cache external to the processor that is not part of the physical ram.  I cannot find any reference to this so I am concerned that it is eating up a good portion of my main memory.  If it is, then I am bumping up to my limit of 16 GBs.  If not, then I have memory to spare, even with all of the apps, tabs, and windows that I have open.

 

Unfortunately, the Activity Monitor Help page makes no mention of cache.

Mac mini, OS X Yosemite (10.10.5)

Posted on Aug 27, 2015 6:13 AM

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Q: Where is the cache shown on the Activity Monitor stored?

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  • by Nubz N.,Helpful

    Nubz N. Nubz N. Aug 28, 2015 11:15 AM in response to Whickwithy
    Community Hosts
    Aug 28, 2015 11:15 AM in response to Whickwithy

    Hey Whickwithy,

     

     

     

    Good question. What is that [Memory] Cache Activity Monitor is showing and where is it?

     

     

     

    Turns out it is memory that was used by apps that is now free to be used by other Apps.  It is "remembered" however so if the original app needs it, it's quickly available.

     

     

     

    See  Use Activity Monitor on your Mac - Apple Support

     

    Cached Files: Memory that was recently used by apps and is now available for use by other apps. For example, if you've been using Mail and then quit Mail, the RAM that Mail was using becomes part of the memory used by cached files, which then becomes available to other apps. If you open Mail again before its cached-files memory is used (overwritten) by another app, Mail opens more quickly because that memory is quickly converted back to app memory without having to load its contents from your startup drive.

     

     

     

    So again, it is Free Memory, but just in case it's needed again, it's remembered or "cached" unless written over by another app or the system.

     

     

     

    Take care.

  • by Whickwithy,

    Whickwithy Whickwithy Aug 28, 2015 11:27 AM in response to Nubz N.
    Level 1 (68 points)
    Mac OS X
    Aug 28, 2015 11:27 AM in response to Nubz N.

    Yeah, thanks.  Even more important, it is part of the total shown for "Memory used".  The way it is shown, that is not clear.  I guess it is part of the "App memory" on the right-hand side rather than the "Wired Memory".  But, most important, I've got plenty of memory to spare!!  It's pretty amazing.  I've got so many apps and windows open it's pretty staggering and the mini-mac isn't even breathing hard.

     

    Thanks again...

  • by Nubz N.,Solvedanswer

    Nubz N. Nubz N. Aug 29, 2015 6:40 AM in response to Whickwithy
    Community Hosts
    Aug 29, 2015 6:40 AM in response to Whickwithy

    Hi Whickwithy,

     

    The Cached Files (now called just Cache) is separate from App Memory or Wired Memory.  Note how the dividing line between the Columns in the lower chart show that App Memory, Wired Memory and Compressed is actually a breakout, details of Memory Used.  Cached Files is listed separately.

     

    Memory pane

     

    The Cached Files is Free Memory that was previously used.  It will decrease if currently running Apps need the memory and there is no more previously unused memory available.

     

    Yes, it's pretty cool.

  • by Whickwithy,

    Whickwithy Whickwithy Aug 29, 2015 7:16 AM in response to Nubz N.
    Level 1 (68 points)
    Mac OS X
    Aug 29, 2015 7:16 AM in response to Nubz N.

    I see.  Thanks.

  • by Whickwithy,

    Whickwithy Whickwithy Aug 29, 2015 7:12 AM in response to Nubz N.
    Level 1 (68 points)
    Mac OS X
    Aug 29, 2015 7:12 AM in response to Nubz N.

    Hmmm, read through what you wrote, again.  You are actually saying it is unused memory.  Interesting.  Either way, the good news is that Memory Used really is the total of the physical memory that is currently in use.

     

    I couldn't get to your link, for some reason.