#!/usr/bin/env perl

use strict;
use Time::HiRes qw(gettimeofday tv_interval);
use POSIX 'strftime';


sub read_proc {
    my %stats = ();
    my @io_files = glob "/proc/**/io";

    foreach (@io_files) {
        /\/proc\/(\d+)\/io/ or next;

        my $pid = $1;
        my %s = ();

        open(FIN, $_) or die "$!";
        while (<FIN>) {
            /^(write|read)_bytes: (\d+)$/ or next;
            $s{$1} = int($2);
        }
        close(FIN);

        $stats{$1} = \%s;
    }

    return %stats;
}

sub assoc_proc_name {
    my $stats = $_[0];

    my $ps = `ps -ef`;
    foreach (split /\n/, $ps) {
        my @c = split(/\s+/, $_);

        next if $c[0] eq "UID";

        $$stats{$c[1]}{"proc"} = join(" ", @c[7..$#c]);
    }
}

sub diff_stats {
    my $stats_now = $_[0];
    my $stats_prev = $_[1];
    my @stats_diff = ();

    foreach (keys(%$stats_now)) {
        next if not exists($$stats_prev{$_});

        my %s = ();
        $s{"pid"} = $_;
        $s{"proc"} = $$stats_now{$_}{"proc"};
        $s{"write"} = $$stats_now{$_}{"write"} - $$stats_prev{$_}{"write"};
        $s{"read"} = $$stats_now{$_}{"read"} - $$stats_prev{$_}{"read"};
        push(@stats_diff, \%s);
    }

    return @stats_diff;
}


my $first_time = 1;
my %stats_prev;
my $time;

while (1) {

    my %stats = &read_proc;
    &assoc_proc_name(\%stats);

    if (!$first_time) {
        my @stats_diff = &diff_stats(\%stats, \%stats_prev);
        my $elapsed = tv_interval($time);
        my $unit = 1000 * 1000;
        my $now = strftime("%Y/%m/%d %H:%M:%S", localtime);

        @stats_diff = sort {($a->{"write"} + $a->{"read"}) <=> ($b->{"write"} + $b->{"read"})} @stats_diff;

        print "=== [" . $now . "] ===\n";
        foreach (@stats_diff) {
            print $$_{"proc"} . ": (w) " . $$_{"write"} / ($elapsed * $unit) . "[MB/s], (r) " . $$_{"read"} / ($elapsed * $unit) . "[MB/s]\n";
        }
    }

    %stats_prev = %stats;
    $time = [gettimeofday];
    $first_time = 0;

    sleep 1;
}