Why is there a problem of using memory (or starman) memory?

Question

I have this simple PSGI application (app.psgi).

use strict;
use warnings;

my $app = sub {
    my $mem = `ps -o rss= -p $$`;
    $mem =~ s/^\s*|\s*$//gs;
    return [ 200, [ 'Content-Type' => 'text/text' ], [ $mem ]];
};

I was asked 1000 times and got increased memory usage. Depending on how the server was started, received:

• plackup - memory usage increases from the first 3 requests and remains constant for the next 997 requests

• plackup -r - memory usage randomly rises (not for every request) by 4k.

• starman - as described above, memory usage is randomly increased by 4k, but at a lower speed

The question arises:

• ? , ( starman), , . (, , , -- 100), .
• - ?

- - script :

use strict;
use warnings;
use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(GET => 'http://localhost:5000');

my $old_mem = 0;
print "req#\tmem\n";
foreach my $i (1..1000) {
    my $res = $ua->request($req);
    (my $mem = $res->content) =~ s/\D//g;
    next if( $mem == $old_mem );
    print "$i\t$mem\n";
    $old_mem = $mem;
}

:

plackup                 plackup -r              starman
req#    mem             req#    mem             req#    mem
1       7780            1       3924            1       3280
2       7800            2       4296            5       3728
3       7804            3       4304            8       3280
                        ...                     ...
                        ... deleted             ... deleted
                        ...                     ...
                        839     4596            994     3912
                        866     4600            998     3908
                        962     4604            1000    3912

,

• plackup ?
• plackup -r - 4k (. ) -
• starman - , 5 (3280- > 3912)

:

# cpanm Plack Starman
Plack is up to date. (0.9979)
Starman is up to date. (0.2010)
# perl -v

This is perl 5, version 12, subversion 3 (v5.12.3) built for darwin-thread-multi-2level

Answer 1

miyagava :

"plackup - 3 997 " . . - miyagawa 14

Starman keep-alive HTTP-, 1000 . ApacheBench - , /-, , . - 14

.

Answer 2

? .

"plackup":

sidburn@sid:~/perl/plack$ ./memory.pl 
req#    mem
1   5340
2   5380

"plackup -r":

sidburn@sid:~/perl/plack$ ./memory.pl 
req#    mem
1   4860
2   5060

"starman":

sidburn@sid:~/perl/plack$ ./memory.pl 
req#    mem
1   5176
5   5224
6   5176
7   5224

:
Perl: 5.12.1 5.12.3
Plack: 0.9979
Starman: 0.2010