Dear Perlmonks, I wrote a (larger) script using perl 5.10.1 and ithreads. This script creates new threads at a certain rate to achieve a asynchronous execution. Although the threads are joined and only a specific number of threads is allowed to run at a time the memory usage of the perl interpreter process increases over time. This increase is more or less linear:

time/s    virtual  residential    
00:00:00  16504     8428
00:01:00  17528     9468
00:02:00  17656    10292
00:03:00  18680    10740
00:04:00  18680    11536
00:05:00  19704    12228
00:06:00  20728    12916
00:07:00  21752    13812
00:08:00  21752    14288
00:09:00  23800    14964
00:10:00  23800    16108
00:11:00  23800    16380
00:12:00  24824    17168
00:13:00  25848    17912
00:14:00  26872    18760
00:15:00  26872    19228
00:16:00  27896    20164
00:17:00  28920    20860
00:18:00  29944    21688
00:19:00  30968    22592
00:20:00  30968    23328
00:21:00  31992    24060
00:22:00  31992    24696
00:23:00  33016    25328
00:24:00  34040    26140
00:25:00  35064    26812
00:26:00  35064    27780
00:27:00  36088    28340
00:28:00  37112    29272
00:29:00  38136    30084
00:30:00  38136    30856
00:31:00  39160    31368
00:32:00  40184    32268
00:33:00  41208    33032
[download]

Any idea how to prevent the script from using more and more memory? The script below is a stripped down version of the original script:

#!/usr/bin/perl

use strict;
use warnings;

use Config;
use threads;

use Time::HiRes qw( usleep );

$Config{useithreads} or die('Recompile Perl with threads to run this p
+rogram.');

foreach my $i (1 .. 100000) {
        while ((my $nthreads = scalar  threads->list()) >= 10) {
                print $nthreads . " running. waiting 1 second.\n";
                sleep(1);

                foreach my $thread (threads->list(threads::joinable)) 
+{
                        $thread->join();
                }
        }

        threads->create(\&sub1);

        usleep(333333);

        foreach my $thread (threads->list(threads::joinable)) {
                $thread->join();
        }
}

foreach my $thread (threads->list()) {
        $thread->join();
}

sub sub1 {
        my $sleep_value = int(rand(2) * 100) / 100;
        print "thread id " . threads->tid() . ": Start sleeping " . $s
+leep_value . " seconds\n";
        usleep($sleep_value * 1000000);
        print "thread id " . threads->tid() . ": Done  sleeping " . $s
+leep_value . " seconds\n";
}
[download]

Details of perl interpreter:

Summary of my perl5 (revision 5 version 10 subversion 1) configuration
+:

  Platform:
    osname=freebsd, osvers=8.2-release, archname=i386-freebsd-thread-m
+ulti-64int
    uname='freebsd hal.hsh 8.2-release freebsd 8.2-release #0: wed feb
+ 23 11:54:06 cet 2011 dirk@hal.hsh:exportobjusrsrcsyshal i386 '
    config_args='-sde -Dprefix=/usr/local -Darchlib=/usr/local/lib/per
+l5/5.10.1/mach -Dprivlib=/usr/local/lib/perl5/5.10.1 -Dman3dir=/usr/l
+ocal/lib/perl5/5.10.1/perl/man/man3 -Dman1dir=/usr/local/man/man1 -Ds
+itearch=/usr/local/lib/perl5/site_perl/5.10.1/mach -Dsitelib=/usr/loc
+al/lib/perl5/site_perl/5.10.1 -Dscriptdir=/usr/local/bin -Dsiteman3di
+r=/usr/local/lib/perl5/5.10.1/man/man3 -Dsiteman1dir=/usr/local/man/m
+an1 -Ui_malloc -Ui_iconv -Uinstallusrbinperl -Dcc=cc -Duseshrplib -Di
+nc_version_list=none -Dccflags=-DAPPLLIB_EXP="/usr/local/lib/perl5/5.
+10.1/BSDPAN" -Doptimize=-O2 -pipe -fno-strict-aliasing -Ud_dosuid -Ui
+_gdbm -Dusethreads=y -Dusemymalloc=n -Duse64bitint -Dusemultiplicity=
+y'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=und
+ef
    use64bitint=define, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
[...]
[download]