Does Lion Have a Memory Leak?

Discussion in 'Apple' started by Charles H. Sampson, May 21, 2014.

  1. Does Lion have a memory leak? I have a one-year old MacBook Pro
    that came with Lion. It has three users and most of the time all of them
    are logged on. This is not an issue with Unix, which I used for years
    professionally, and it's not an issue with my old G4 that runs Tiger.
    (Yes, the G4 runs slowly but it's not affected by the number of users
    logged on. If a user is running a compute hog, that's another story.)

    Every once in a while, at least once a week it seems, the MacBook
    runs glacially slow. The only fix that I've discovered so far is to log
    everybody off and restart. Then all is good, at least for a while.

    Charles H. Sampson, May 21, 2014
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  2. A leak should show up as a process's virtual memory size growing without
    ever leveling off. It should be easy to find.

    10.7 and 10.8 have some bad virtual memory tuning. Somebody figured
    that the computer would be faster if one app could not cause another app
    to page out, so Lion gives each process a limited amount of RAM. What
    actually happens is that a process needing a lot of RAM produces so much
    swapping that the boot disk is unusably slow for the entire system. The
    cause of this type of slowdown doesn't show up well in 'top' or Activity

    10.9 mostly fixes the problem.

    Memory can become fragmented but I think only 10.6 and earlier can get a
    severe case of it. Only certain use cases can cause it.
    Kevin McMurtrie, May 21, 2014
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  3. Yes. Activity Monitor shows no CPU hogs and the amount of disk and
    network activity seem quite reasonable.

    Charles H. Sampson, May 22, 2014
  4. As time permits, I'll check this out. First I'll have to write down
    what the startup VM sizes of our common applications are (there are only
    a few of them), then use that to check when the problem occurs.
    Somebody figured out wrong. If you implement virtual memory using a
    least-recently-used (LRU) swapping strategy the system tunes itself on
    the fly, depending on memory usage at the time. This is well-known. Of
    course, if you don't have enough real memory for what you're trying to
    do, then you get a lot of swapping out and reading back in, a condition
    known as thrashing. In that case, you have either an insufficient memory
    problem or a usage problem and the fix is to get more memory or stop
    overloading you computer. (If you already know this, please forgive me
    for being so professorial.)
    I heard elsewhere that Lion is not very good and I should upgrade
    to Mountain Lion. Apple wants me to go to Maverick (for free). I've
    started looking into that.
    Thanks for your help.

    Charles H. Sampson, May 22, 2014
  5. No direct evidence. Just a shot in the dark trying to come up with
    an explanation for the slowing down.

    Charles H. Sampson, May 23, 2014
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