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Re: Avoiding memory loss...

by Anonymous Monk
on Dec 27, 2012 at 22:33 UTC ( #1010587=note: print w/ replies, xml ) Need Help??


in reply to Avoiding memory loss...

... but they probably won't be destroyed immediately. Like most systems, Perl is "lazy." Unreferenced items are marked for deletion but nothing actually happens until the garbage-collector makes its midnight run, banging the cans together and waking everybody up.


Comment on Re: Avoiding memory loss...
Re^2: Avoiding memory loss...
by J.Perl.Man (Novice) on Dec 27, 2012 at 22:41 UTC

    So perhaps I'm right to be concerned about cleanup... the program itself will be installed as a daemon, so anything I can do to prevent long term consumption, or to force garbage collection would be good.

    What method do you recommend to remove the array? My read of delete (man page) against an array leads me to believe that I'm still waiting on true garbage collection

      > So perhaps I'm right to be concerned about cleanup

      No don't worry, Anonymous probably confuses the garbage collection systems.

      Perl doesn't freeze!

      Just be careful to not produce circular references.

      Cheers Rolf

Re^2: Avoiding memory loss...
by dave_the_m (Parson) on Dec 27, 2012 at 23:29 UTC
    but nothing actually happens until the garbage-collector makes its midnight run
    No, perl doesn't use a garbage collector. Items are freed immediately when their ref count goes to zero.

    Dave.

      > No, perl doesn't use a garbage collector.

      most probably a problem of fuzzy terminology¹, perldoc talks about "garbage collection":

       Perl uses a fast and simple, reference-based garbage collection system

      see perlobj#Two-Phased-Garbage-Collection

      But as opposed to mark-and-sweep Perl's runtime approach is very simple an efficient.

      OTOH it can't handle circular references.

      And even if mark-and-sweep was used, IIRC Python does it and is still very performant. ²

      Cheers Rolf

      UPDATES:

      ¹) from perlglossary

      garbage collection A misnamed feature--it should be called, "expecting your mo +ther to pick up after you". Strictly speaking, Perl doesn’t do thi +s, but it relies on a reference-counting mechanism to keep things +tidy. However, we rarely speak strictly and will often refer to t +he reference-counting scheme as a form of garbage collection. + (If it’s any comfort, when your interpreter exits, a "real" gar +bage collector runs to make sure everything is cleaned up if you +’ve been messy with circular references and such.)

      ²) more complicated: "While Python uses the traditional reference counting implementation, it also offers a cycle detector that works to detect reference cycles."

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