Active memory doesn't go inactive

Discussion in 'macOS' started by Schtibbie, Mar 7, 2009.

  1. Schtibbie macrumors 6502

    Jan 13, 2007
    YES, I am aware of the definitions and supposed behaviors of free mem, active, inactive, wired, when looking at Activity Monitor. I know that Leopard caches stuff, yada yada yada...

    BUT.. I just doubled my RAM from 1 to 2 gigs. After a fresh boot and loading up Safari, Firefox, and iPhoto, and then CLOSING all of them and running no apps, Leopard shows more than a gig of ACTIVE memory, which even after sitting there for an hour doing nothing - does NOT go over to the INactive section. Why? I'm not asking why it doesn't go to "free". I know why.

    My top command output:
    PhysMem: 240M wired, 1006M active, 307M inactive, 1559M used, 489M free.
    VM: 5579M + 374M 276396(0) pageins, 61(0) pageouts
  2. ihabime macrumors 6502

    Jan 12, 2005
    It doesn't pass back to inactive because technically it's not, the OS holds it as cache in case you relaunch those apps.

    It is still available to be used by other applications if they need it though.

    The labels are a bit misleading, they really describe the priority that the OS will use to decide where to grab from, first free then inactive then active. In the case of active memory it might even swap the contents to disk if it contains a currently running app.
  3. ElectricSheep macrumors 6502


    Feb 18, 2004
    Wilmington, DE
    That is because the kernel doesn't actually maintain these lists (in the sense of moving old active pages to the inactive list, and paging inactive objects out to disk) until the number of free physical pages hits a low-water mark.
  4. Schtibbie thread starter macrumors 6502

    Jan 13, 2007
    Ah, makes sense! I guess there's no point shuffling pages around just for fun until it's needed.

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