Yeah. I wish I understood, or one of the guys that know would tell us, where the memory growth actually arises.

If you run this (having substituted a suitable mem routine for your platform), and then play with the various values, it's really difficult to devine where the growth occurs and what controls how much? 

#! perl -slw
use strict;
use Data::Dumper;
use threads;
use threads::shared;
no warnings 'misc';

our $N ||= 100;
our $D ||= 1.e5;
our $SHARED;

sub mem {
    my @filler          = 1 .. $D unless @_;
    my @filler : shared = 1 .. $D if @_;
    my( $usage ) =  `tasklist /NH /FI \"pid eq $$\" ` =~ m[ (\S+) \s+ 
+K \s* $ ]x;
    $usage =~ tr[,][]d;
    return 1024 * $usage;
}

my @data        = 1 .. $D unless $SHARED;
my @data:shared = 1 .. $D if $SHARED;

printf "start : %6d\n", my $start = mem;
for ( 1 .. $N ) {
    my $thread = threads->create( \&mem );
    printf "%3d   : %6d\n", $_, $thread->join;
}
printf "end   : %6d\n", my $end = mem;
printf "Growth:  %6d\n", $end - $start;

[download]

Here are some typical results on my system:

c:\test\fork>..\534254 -N=10 -D=1
start : 3141632
  1   : 3993600
  2   : 4018176
  3   : 4018176
  4   : 4022272
  5   : 4038656
  6   : 4038656
  7   : 4022272
  8   : 4018176
  9   : 4055040
 10   : 4055040
end   : 4034560
Growth:  892928

c:\test\fork>..\534254 -N=10 -D=1 -SHARED
start : 3145728
  1   : 3997696
  2   : 4022272
  3   : 4022272
  4   : 4030464
  5   : 4026368
  6   : 4022272
  7   : 4059136
  8   : 4059136
  9   : 4059136
 10   : 4059136
end   : 4042752
Growth:  897024

c:\test\fork>..\534254 -N=10 -D=1e3
start : 3211264
  1   : 4128768
  2   : 4149248
  3   : 4149248
  4   : 4157440
  5   : 4149248
  6   : 4153344
  7   : 4157440
  8   : 4161536
  9   : 4157440
 10   : 4198400
end   : 4132864
Growth:  921600

c:\test\fork>..\534254 -N=10 -D=1e3 -SHARED
start : 3555328
  1   : 4345856
  2   : 4378624
  3   : 4382720
  4   : 4386816
  5   : 4395008
  6   : 4390912
  7   : 4390912
  8   : 4390912
  9   : 4386816
 10   : 4395008
end   : 4374528
Growth:  819200

c:\test\fork>..\534254 -N=10 -D=1e5
start : 9723904
  1   : 17874944
  2   : 17907712
  3   : 17920000
  4   : 17940480
  5   : 17924096
  6   : 17940480
  7   : 17936384
  8   : 17944576
  9   : 17936384
 10   : 17952768
end   : 11743232
Growth:  2019328

c:\test\fork>..\534254 -N=10 -D=1e5 -SHARED
start : 43819008
  1   : 48697344
  2   : 48721920
  3   : 48726016
  4   : 48726016
  5   : 48730112
  6   : 48730112
  7   : 48730112
  8   : 48734208
  9   : 48738304
 10   : 48738304
end   : 44195840
Growth:  376832

[download]
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^2: threads: spawn early to avoid the crush. by BrowserUk
in thread threads: spawn early to avoid the crush. by BrowserUk

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