Re: Perl releasing memory back to the system

AFAIK, perl 5.8.6 (and probably a couple of earlier versions) can release memory back to the system on Linux.

#!/usr/local/bin/perl -w
use strict;
$|=1;
{
    my $string;
    for (1 .. 100000) {
        $string .= ('x' x 1000);
    }
    print "press enter to release";
    <>;
    undef $string; # note that memory does not get released
                   # if the variable only goes out of scope.
                   # you *need* to undef it!
}

print "ok, press enter to exit";
<>;
[download]

This takes up roughly a 100 Mb on my machine, and almost all of it gets released after the first enter. (according to top, at least)

perl -V
Summary of my perl5 (revision 5 version 8 subversion 6) configuration:
  Platform:
    osname=linux, osvers=2.6.8.20050102, archname=i686-linux
[download]

    uname='linux sepia 2.6.8.20050102 #1 sun jan 2 14:47:32 cet 2005 i
+686 gnulinux '
    config_args='-DDEBUGGING -DLEAKTEST'
    hint=previous, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultipl
+icity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -pipe -I/usr/local/include
+ -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-g -DDEBUGGING -DLEAKTEST',
    cppflags='-fno-strict-aliasing -pipe -I/usr/local/include -fno-str
+ict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_O
+FFSET_BITS=64 -fno-strict-aliasing -pipe -I/usr/local/include -D_LARG
+EFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    ccversion='', gccversion='3.3.5 (Debian 1:3.3.5-8)', gccosandvers=
+''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+2
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -ldb -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.3.2.so, so=so, useshrplib=false, libperl=libperl.
+a
    gnulibc_version='2.3.2'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: DEBUGGING USE_LARGE_FILES
  Built under linux
  Compiled at Mar 15 2005 20:40:51
  @INC:
    /usr/local/lib/perl5/5.8.6/i686-linux
    /usr/local/lib/perl5/5.8.6
    /usr/local/lib/perl5/site_perl/5.8.6/i686-linux
    /usr/local/lib/perl5/site_perl/5.8.6
    /usr/local/lib/perl5/site_perl
[download]

"What should it profit a man, if he should win a flame war, yet lose his cool?"

Comment on Re: Perl releasing memory back to the system Select or Download Code

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Re^2: Perl releasing memory back to the system by zentara (Cardinal) on Apr 07, 2005 at 20:00 UTC
Thanks! Great example, works for me. It is the first time I've seen this demonstrated with Perl. :-) I'm not really a human, but I play one on earth. flash japh	[reply]