Can anybody explain why this code doesn't do what I think it should?


use strict;
sleep 5;

if (1) { my $foo = "perl" x 1000000;  sleep 5; }
if (1) { my $foo = "perl" x 1000000;  sleep 5; }
if (1) { my $foo = "perl" x 1000000;  sleep 5; }
if (1) { my $foo = "perl" x 1000000;  sleep 5; }
if (1) { my $foo = "perl" x 1000000;  sleep 5; }
if (1) { my $foo = "perl" x 1000000;  sleep 5; }

[download]
I always thought that if you declare a lexical variable (such as my $foo) inside a block, that it gets freed / garbage-collected at the end of the block.

My understanding is that while perl may not return allocated memory back to the OS, it will at least reuse earlier freed memory, rather than allocating more from the OS.

However, the code above will grow by 8M every 5 seconds. If you include the if-loop enough times, it will consume all available memory (at least on Win2k, perl 5.6.1 and 5.8.0)

In reply to Strange memory growth? by meetraz

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.