use warnings;
use strict;
use Fcntl;
use Time::HiRes qw/time/;
use Parallel::ForkManager;

my $runtime = 5;  ## desired runtime, in seconds
my $nprocs = 0;

sub gen_pks {
    my ($npks) = @_;
    my @pks;
   
    sysopen my $fd, '/dev/urandom', O_RDONLY;
    for (1..$npks) {
        my $read = sysread $fd, my $buf, 256/8 or die "sysread: $!";
        die 'EOF' unless $read;
        warn 'short read' if 256/8 != length $buf;
        push @pks, $buf
    }
    close $fd;

    return \@pks;
}

sub ncpus {
    open my $fd, '<', '/proc/cpuinfo' or die "open: $!";
    my $ncpus = grep { /^processor/ } <$fd>;
    close $fd;
    return $ncpus;
}

my $t0 = time;
my $pm = Parallel::ForkManager->new ($nprocs or ncpus);
$pm->set_waitpid_blocking_sleep (0);
$pm->run_on_finish (sub {
    my $data = pop;
    printf "%s\n", unpack 'H*', $_ for @$data;
});

while (1) {
    last if time-$t0 > $runtime;
    $pm->start and next;
    $pm->finish (0, gen_pks 1e3);
}
$pm->wait_all_children;