Interesting. FWIW, on Windows 7 (monitoring with Task Manager) and running Strawberry 5.14.2.1, the program below will release (very) roughly half of the allocated memory when the undef $s is done. If the  undef statement is changed to  $s = ''; nothing is deallocated.

Half?!? What this means I do not know. (But see Update2 below.) 

>perl -wMstrict -le
"my $s = '.' x 500_000_000;
 sleep 5;
 undef $s;
 sleep 10;
"

[download]

Update: Same results with Strawberry 5.10.1.5.

Update2: Actually, I think I understand a little of what is going on. From the Task Manager memory stats, when the  '.' x 500_000_000 expression of the  my $s = '.' x 500_000_000; statement executes, it consumes about 500M to build the string. The string is then copied to the  $s scalar, thus consuming another 500M, for a total of 1G. It appears the first 500M (used to build the string) is never deallocated. Only the memory consumed by the  $s scalar is deallocated when it is undef-ed.

In reply to Re^4: Memory management with long running scripts by AnomalousMonk
in thread Memory management with long running scripts by jamesrleu

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.