#!/usr/bin/perl --
use strict;
use warnings;
use Path::Tiny qw/ path /;
use File::Map qw' map_file advise ';

eval { do 'memusage-workingset-virtualmemory.pl'; 1 } or warn $@;

sub memusage() { print mems($$), "\n"; }

my $filename = 'goner-is-gone.txt';
my $fh       = path($filename)->openw_raw;
print $fh "01234567789abcdefghijklmnopqrstuvwxyz\n" for 1 .. 1_400_000;
close $fh;
print -s $filename, "\n";
memusage();
{
    map_file my $map, $filename, '+<';
    memusage();

#~     advise( $map, 'sequential' ); ## no visible difference in pslist from normal
#~     advise( $map, 'random' ); ## same
    memusage();
    my @intervals =
      map { $_ * ( 1024 * 1024 ) } 1 .. 100;   ## after every mb print something
    my $lpos = 0;
    while ( $map =~ m{z}g ) {
        my $pos = pos($map);
        $lpos = $pos;
        next if $pos < $intervals[0];
        shift @intervals;
        print 'pos ', $pos, "\n";
        memusage();
    }
    print "last pos $lpos\n";
    memusage();

    #~     <>;

}

memusage();

path($filename)->remove;

__END__
53200000
WVM: 21952 { WS: 6164 VM: 3344 } 
WVM: 73908 { WS: 6200 VM: 3444 } 
WVM: 73908 { WS: 6200 VM: 3444 } 
pos 1048609
WVM: 73908 { WS: 7236 VM: 3456 } 
pos 2097181
WVM: 73908 { WS: 8264 VM: 3456 } 
pos 3145753
WVM: 73908 { WS: 9292 VM: 3456 } 
pos 4194325
WVM: 73908 { WS: 10320 VM: 3456 } 
pos 5242897
WVM: 73908 { WS: 11344 VM: 3456 } 
pos 6291469
WVM: 73908 { WS: 12372 VM: 3456 } 
pos 7340041
WVM: 73908 { WS: 13400 VM: 3456 } 
pos 8388613
WVM: 73908 { WS: 14428 VM: 3456 } 
pos 9437185
WVM: 73908 { WS: 15452 VM: 3456 } 
pos 10485795
WVM: 73908 { WS: 16480 VM: 3456 } 
pos 11534367
WVM: 73908 { WS: 17508 VM: 3456 } 
pos 12582939
WVM: 73908 { WS: 18536 VM: 3456 } 
pos 13631511
WVM: 73908 { WS: 19560 VM: 3456 } 
pos 14680083
WVM: 73908 { WS: 20588 VM: 3456 } 
pos 15728655
WVM: 73908 { WS: 21616 VM: 3456 } 
pos 16777227
WVM: 73908 { WS: 22644 VM: 3456 } 
pos 17825799
WVM: 73908 { WS: 23668 VM: 3456 } 
pos 18874371
WVM: 73908 { WS: 24696 VM: 3456 } 
pos 19922981
WVM: 73908 { WS: 25724 VM: 3456 } 
pos 20971553
WVM: 73908 { WS: 26752 VM: 3456 } 
pos 22020125
WVM: 73908 { WS: 27776 VM: 3456 } 
pos 23068697
WVM: 73908 { WS: 28804 VM: 3456 } 
pos 24117269
WVM: 73908 { WS: 29832 VM: 3456 } 
pos 25165841
WVM: 73908 { WS: 30860 VM: 3456 } 
pos 26214413
WVM: 73908 { WS: 31884 VM: 3456 } 
pos 27262985
WVM: 73908 { WS: 32912 VM: 3456 } 
pos 28311557
WVM: 73908 { WS: 33940 VM: 3456 } 
pos 29360129
WVM: 73908 { WS: 34968 VM: 3456 } 
pos 30408739
WVM: 73908 { WS: 35992 VM: 3456 } 
pos 31457311
WVM: 73908 { WS: 37020 VM: 3456 } 
pos 32505883
WVM: 73908 { WS: 38048 VM: 3456 } 
pos 33554455
WVM: 73908 { WS: 39076 VM: 3456 } 
pos 34603027
WVM: 73908 { WS: 40100 VM: 3456 } 
pos 35651599
WVM: 73908 { WS: 41128 VM: 3456 } 
pos 36700171
WVM: 73908 { WS: 42156 VM: 3456 } 
pos 37748743
WVM: 73908 { WS: 43184 VM: 3456 } 
pos 38797315
WVM: 73908 { WS: 44208 VM: 3456 } 
pos 39845925
WVM: 73908 { WS: 45236 VM: 3456 } 
pos 40894497
WVM: 73908 { WS: 46268 VM: 3456 } 
pos 41943069
WVM: 73908 { WS: 47296 VM: 3456 } 
pos 42991641
WVM: 73908 { WS: 48320 VM: 3456 } 
pos 44040213
WVM: 73908 { WS: 49348 VM: 3456 } 
pos 45088785
WVM: 73908 { WS: 50376 VM: 3456 } 
pos 46137357
WVM: 73908 { WS: 51404 VM: 3456 } 
pos 47185929
WVM: 73908 { WS: 52428 VM: 3456 } 
pos 48234501
WVM: 73908 { WS: 53456 VM: 3456 } 
pos 49283073
WVM: 73908 { WS: 54484 VM: 3456 } 
pos 50331683
WVM: 73908 { WS: 55512 VM: 3456 } 
pos 51380255
WVM: 73908 { WS: 56536 VM: 3456 } 
pos 52428827
WVM: 73908 { WS: 57564 VM: 3456 } 
last pos 53199999
WVM: 73908 { WS: 58320 VM: 3456 } 
WVM: 21952 { WS: 6264 VM: 3356 }