parallel/src/niceload

#!/usr/bin/perl -w

# Copyright (C) 2004,2005,2006,2006,2008,2009,2010 Ole Tange,
# http://ole.tange.dk
#
# Copyright (C) 2010,2011 Ole Tange, http://ole.tange.dk and Free
# Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>
# or write to the Free Software Foundation, Inc., 51 Franklin St,
# Fifth Floor, Boston, MA 02110-1301 USA

use strict;
use Getopt::Long;
$Global::progname="niceload";
$Global::version = 20121122;
Getopt::Long::Configure("bundling","require_order");
get_options_from_array(\@ARGV) || die_usage();
if($::opt_version) {
    version();
    exit 0;
}
if($::opt_help) {
    help();
    exit 0;
}
if($::opt_factor and $::opt_suspend) {
    # You cannot have --suspend and --factor
    help();
    exit;
}
if(not (defined $::opt_start_io or defined $::opt_run_io
	or defined $::opt_start_load or defined $::opt_run_load
	or defined $::opt_start_mem or defined $::opt_run_mem
	or defined $::opt_start_noswap or defined $::opt_run_noswap
	or defined $::opt_io or defined $::opt_load
	or defined $::opt_mem or defined $::opt_noswap)) {
    # Default is --runload=1
    $::opt_run_load = 1;
}

if(not defined $::opt_start_io) { $::opt_start_io = $::opt_io; }
if(not defined $::opt_run_io) { $::opt_run_io = $::opt_io; }
if(not defined $::opt_start_load) { $::opt_start_load = $::opt_load; }
if(not defined $::opt_run_load) { $::opt_run_load = $::opt_load; }
if(not defined $::opt_start_mem) { $::opt_start_mem = $::opt_mem; }
if(not defined $::opt_run_mem) { $::opt_run_mem = $::opt_mem; }
if(not defined $::opt_start_noswap) { $::opt_start_noswap = $::opt_noswap; }
if(not defined $::opt_run_noswap) { $::opt_run_noswap = $::opt_noswap; }

if(defined $::opt_load) { multiply_binary_prefix($::opt_load); }

my $limit = Limit->new();
my $process = Process->new($::opt_nice,@ARGV);
if($::opt_pid) {
    $process->set_pid($::opt_pid);
} elsif (@ARGV) {
    # Wait until limit is below start_limit and run_limit
    while($limit->over_start_limit()
	  or
	  ($limit->hard() and $limit->over_run_limit())) {
	$limit->sleep_for_recheck();
    }
    $process->start();
}

while($process->is_alive()) {
    if($limit->over_run_limit()) {
	$process->suspend();
	$limit->sleep_for_recheck();
	if(not $limit->hard()) {
	    $process->resume();
	    $limit->sleep_while_running();
	}
    } else {
	$process->resume();
	$limit->sleep_while_running();
    }
}

exit($::exitstatus);

sub multiply_binary_prefix {
    # Evalualte numbers with binary prefix
    # k=10^3, m=10^6, g=10^9, t=10^12, p=10^15, e=10^18, z=10^21, y=10^24
    # K=2^10, M=2^20, G=2^30, T=2^40, P=2^50, E=2^70, Z=2^80, Y=2^80
    # Ki=2^10, Mi=2^20, Gi=2^30, Ti=2^40, Pi=2^50, Ei=2^70, Zi=2^80, Yi=2^80
    # ki=2^10, mi=2^20, gi=2^30, ti=2^40, pi=2^50, ei=2^70, zi=2^80, yi=2^80
    # 13G = 13*1024*1024*1024 = 13958643712
    my $s = shift;
    $s =~ s/k/*1000/g;
    $s =~ s/M/*1000*1000/g;
    $s =~ s/G/*1000*1000*1000/g;
    $s =~ s/T/*1000*1000*1000*1000/g;
    $s =~ s/P/*1000*1000*1000*1000*1000/g;
    $s =~ s/E/*1000*1000*1000*1000*1000*1000/g;
    $s =~ s/Z/*1000*1000*1000*1000*1000*1000*1000/g;
    $s =~ s/Y/*1000*1000*1000*1000*1000*1000*1000*1000/g;
    $s =~ s/X/*1000*1000*1000*1000*1000*1000*1000*1000*1000/g;

    $s =~ s/Ki?/*1024/gi;
    $s =~ s/Mi?/*1024*1024/gi;
    $s =~ s/Gi?/*1024*1024*1024/gi;
    $s =~ s/Ti?/*1024*1024*1024*1024/gi;
    $s =~ s/Pi?/*1024*1024*1024*1024*1024/gi;
    $s =~ s/Ei?/*1024*1024*1024*1024*1024*1024/gi;
    $s =~ s/Zi?/*1024*1024*1024*1024*1024*1024*1024/gi;
    $s =~ s/Yi?/*1024*1024*1024*1024*1024*1024*1024*1024/gi;
    $s =~ s/Xi?/*1024*1024*1024*1024*1024*1024*1024*1024*1024/gi;
    $s = eval $s;
    return $s;
}

sub get_options_from_array {
    # Run GetOptions on @array
    # Returns:
    #   true if parsing worked
    #   false if parsing failed
    #   @array is changed
    my $array_ref = shift;
    # A bit of shuffling of @ARGV needed as GetOptionsFromArray is not
    # supported everywhere
    my @save_argv;
    my $this_is_ARGV = (\@::ARGV == $array_ref);
    if(not $this_is_ARGV) {
	@save_argv = @::ARGV;
	@::ARGV = @{$array_ref};
    }
    my @retval = GetOptions
	("debug|D" => \$::opt_debug,
	 "factor|f=s" => \$::opt_factor,
	 "hard|H" => \$::opt_hard,
	 "soft|S" => \$::opt_soft,
	 "sensor=s" => \$::opt_sensor,

	 "si|sio|startio|start-io=s" => \$::opt_start_io,
	 "ri|rio|runio|run-io=s" => \$::opt_run_io,
	 "io|I=s" => \$::opt_io,

	 "sl|startload|start-load=s" => \$::opt_start_load,
	 "rl|runload|run-load=s" => \$::opt_run_load,
	 "load|L|l=s" => \$::opt_load,

	 "sm|startmem|start-mem=s" => \$::opt_start_mem,
	 "rm|runmem|run-mem=s" => \$::opt_run_mem,
	 "mem|M=s" => \$::opt_mem,

	 "sn|startnoswap|start-noswap|start-no-swap" => \$::opt_start_noswap,
	 "rn|runnoswap|run-noswap|run-no-swap" => \$::opt_run_noswap,
	 "noswap|N" => \$::opt_noswap,

	 "nice|n=i" => \$::opt_nice,
	 "process|pid|p=s" => \$::opt_pid,
	 "suspend|s=s" => \$::opt_suspend,
	 "recheck|t=s" => \$::opt_recheck,
	 "quote|q" => \$::opt_quote,
	 "help|h" => \$::opt_help,
	 "verbose|v" => \$::opt_verbose,
	 "version|V" => \$::opt_version,
	);
    if(not $this_is_ARGV) {
	@{$array_ref} = @::ARGV;
	@::ARGV = @save_argv;
    }
    return @retval;
}


sub die_usage {
    help();
    exit 1;
}


sub help {
    print q{
Usage:
   niceload [-v] [-n niceness] [-L loadavg] [-I io] [-N] [-M mem]
            [-s suspend_sec|-f factor] [-H] [-S]
            command or -p pid
};
}


sub die_bug {
    my $bugid = shift;
    print STDERR
	("$Global::progname: This should not happen. You have found a bug.\n",
	 "Please contact <parallel\@gnu.org> and include:\n",
	 "* The version number: $Global::version\n",
	 "* The bugid: $bugid\n",
	 "* The command line being run\n",
	 "* The files being read (put the files on a webserver if they are big)\n",
	 "\n",
	 "If you get the error on smaller/fewer files, please include those instead.\n");
    exit(255);
}


sub usleep {
    # Sleep this many milliseconds.
    my $secs = shift;
    ::debug("Sleeping ",$secs," millisecs\n");
    select(undef, undef, undef, $secs/1000);
}


sub debug {
    if($::opt_debug) {
	print STDERR @_;
    }
}


sub my_dump {
    # Returns:
    #   ascii expression of object if Data::Dump(er) is installed
    #   error code otherwise
    my @dump_this = (@_);
    eval "use Data::Dump qw(dump);";
    if ($@) {
        # Data::Dump not installed
        eval "use Data::Dumper;";
        if ($@) {
            my $err =  "Neither Data::Dump nor Data::Dumper is installed\n".
                "Not dumping output\n";
            print STDERR $err;
            return $err;
        } else {
            return Dumper(@dump_this);
        }
    } else {
        eval "use Data::Dump qw(dump);";
        return (Data::Dump::dump(@dump_this));
    }
}


sub version {
    # Returns: N/A
    print join("\n",
	       "GNU $Global::progname $Global::version",
	       "Copyright (C) 2004,2005,2006,2007,2008,2009 Ole Tange",
	       "Copyright (C) 2010,2011 Ole Tange and Free Software Foundation, Inc.",
	       "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>",
	       "This is free software: you are free to change and redistribute it.",
	       "GNU $Global::progname comes with no warranty.",
	       "",
	       "Web site: http://www.gnu.org/software/parallel\n"
	);
}


sub max {
    # Returns:
    #   Maximum value of array
    my $max;
    for (@_) {
        # Skip undefs
        defined $_ or next;
        defined $max or do { $max = $_; next; }; # Set $_ to the first non-undef
        $max = ($max > $_) ? $max : $_;
    }
    return $max;
}


package Process;

sub new {
    my $class = shift;
    my $nice = shift;
    my @ARGV = @_;
    if($nice) {
	unshift(@ARGV, "nice", "-n", $nice);
    }
    return bless {
	'running' => 0, # Is the process running now?
	'command' => [@ARGV],
    }, ref($class) || $class;
}

sub set_pid {
    my $self = shift;
    $self->{'pid'} = shift;
    push(@{$self->{'pids'}},$self->{'pid'});
    $self->{'running'} = 1;
    $::exitstatus = 0;
}

sub start {
    # Start the program
    my $self = shift;
    ::debug("Starting @{$self->{'command'}}\n");
    $self->{'running'} = 1;
    if($self->{'pid'} = fork) {
	# set signal handler to kill children if parent is killed
	push @{$self->{'pids'}}, $self->{'pid'};
	$Global::process = $self;
	$SIG{CHLD} = \&REAPER;
	$SIG{INT}=\&kill_child_INT;
	$SIG{TSTP}=\&kill_child_TSTP;
	$SIG{CONT}=\&kill_child_CONT;
 	sleep 1; # Give child time to setpgrp(0,0);
 	$self->{'pgrp'} = getpgrp $self->{'pid'};
    } else {
 	setpgrp(0,0);
 	::debug("Child pid: $$, pgrp: ",getpgrp $$,"\n");
 	::debug("@{$self->{'command'}}\n");
	if($::opt_quote) {
	    system(@{$self->{'command'}});
	} else {
	    system("@{$self->{'command'}}");
	}
	$::exitstatus = $? >> 8;
	$::exitsignal = $? & 127;
	::debug("Child exit $::exitstatus\n");
	exit($::exitstatus);
    }
}

use POSIX ":sys_wait_h";

sub REAPER {
    my $stiff;
    while (($stiff = waitpid(-1, &WNOHANG)) > 0) {
        # do something with $stiff if you want
        $::exitstatus = $? >> 8;
        $::exitsignal = $? & 127;
    }
    $SIG{CHLD} = \&REAPER;                  # install *after* calling waitpid
}


sub kill_child_CONT {
    my $self = $Global::process;
    ::debug("SIGCONT received. Killing $self->{'pid'}\n");
    kill CONT => -getpgrp($self->{'pid'});
}


sub kill_child_TSTP {
    my $self = $Global::process;
    ::debug("SIGTSTP received. Killing $self->{'pid'} and self ($$)\n");
    kill TSTP => -getpgrp($self->{'pid'});
    kill STOP => -$$;
    kill STOP => $$;
}


sub kill_child_INT {
    my $self = $Global::process;
    ::debug("SIGINT received. Killing $self->{'pid'} Exit\n");
    kill INT => -getpgrp($self->{'pid'});
    exit;
}


sub resume {
    my $self = shift;
    ::debug("Resume @{$self->{'pids'}}\n");
    if(not $self->{'running'}) {
	# - = PID group
	map { kill "CONT", -$_ } @{$self->{'pids'}};
	# If using -p it is not in a group
	map { kill "CONT", $_ } @{$self->{'pids'}};
	$self->{'running'} = 1;
    }
}


sub suspend {
    my $self = shift;
    ::debug("Suspend @{$self->{'pids'}}\n");
    if($self->{'running'}) {
	# - = PID group
	map { kill "STOP", -$_ } @{$self->{'pids'}};
	# If using -p it is not in a group
	map { kill "STOP", $_ } @{$self->{'pids'}};
	$self->{'running'} = 0;
    }
}


sub is_alive {
    # The process is dead if none of the pids exist
    my $self = shift;
    my ($exists) = 0;
    for my $pid (@{$self->{'pids'}}) {
	if(kill 0 => $pid) { $exists++ }
    }
    ::debug("is_alive: $exists\n");
    return $exists;
}


package Limit;

sub new {
    my $class = shift;
    my %limits = @_;
    my $hard = $::opt_soft ? 0 : $::opt_hard;
    my $runio = $::opt_run_io ? ::multiply_binary_prefix($::opt_run_io) : 0;
    my $startio = $::opt_start_io ? ::multiply_binary_prefix($::opt_start_io) : 0;
    my $runload = $::opt_run_load ? ::multiply_binary_prefix($::opt_run_load) : 0;
    my $startload = $::opt_start_load ? ::multiply_binary_prefix($::opt_start_load) : 0;
    my $runmem = $::opt_run_mem ? ::multiply_binary_prefix($::opt_run_mem) : 0;
    my $startmem = $::opt_start_mem ? ::multiply_binary_prefix($::opt_start_mem) : 0;
    my $runnoswap = $::opt_run_noswap ? ::multiply_binary_prefix($::opt_run_noswap) : 0;
    my $startnoswap = $::opt_start_noswap ? ::multiply_binary_prefix($::opt_start_noswap) : 0;

    return bless {
	'hard' => $hard,
	'recheck' => 1, # Default
	'runtime' => 1, # Default
	'runio' => $runio,
	'startio' => $startio,
	'runload' => $runload,
	'startload' => $startload,
	'runmem' => $runmem,
	'startmem' => $startmem,
	'runnoswap' => $runnoswap,
	'startnoswap' => $startnoswap,
	'factor' => $::opt_factor || 1,
	'recheck' => $::opt_recheck || 1,
	'runtime' => $::opt_recheck || 1,
	'over_run_limit' => 1,
	'over_start_limit' => 1,
	'verbose' => $::opt_verbose,
    }, ref($class) || $class;
}


sub over_run_limit {
    my $self = shift;
    my $status = 0;
    if($self->{'runmem'}) {
	# mem should be between 0-10ish
	# 100% available => 0 (1-1)
	# 50% available => 1 (2-1)
	# 10% available => 9 (10-1)
	my $mem = $self->mem_status();
	::debug("Run memory: $self->{'runmem'}/$mem\n");
	$status += (::max(1,$self->{'runmem'}/$mem)-1);
    }
    if($self->{'runload'}) {
	# If used with other limits load should be between 0-10ish
	no warnings 'numeric';
	my $load = $self->load_status();
	if($self->{'runload'} > 0) {
	    # Stop if the load is above the limit
	    $status += ::max(0,$load - $self->{'runload'});
	} else {
	    # Stop if the load is below the limit (for sensor)
	    $status += ::max(0,-$load - $self->{'runload'});
	}
    }
    if($self->{'runnoswap'}) {
	# swap should be between 0-10ish
	# swap in or swap out or no swap = 0
	# else log(swapin*swapout)
	my $swap = $self->swap_status();
	$status += log(::max(1, $swap - $self->{'runnoswap'}));
    }
    if($self->{'runio'}) {
	my $io = $self->io_status();
	$status += ::max(0,$io - $self->{'runio'});
    }
    $self->{'over_run_limit'} = $status;
    if(not $::opt_recheck) {
	$self->{'recheck'} = $self->{'factor'} * $self->{'over_run_limit'};
    }
    ::debug("over_run_limit: $status\n");
    return $self->{'over_run_limit'};
}

sub over_start_limit {
    my $self = shift;
    my $status = 0;
    if($self->{'startmem'}) {
	# mem should be between 0-10ish
	# 100% available => 0 (1-1)
	# 50% available => 1 (2-1)
	# 10% available => 9 (10-1)
	my $mem = $self->mem_status();
	::debug("Start memory: $self->{'startmem'}/$mem\n");
	$status += (::max(1,$self->{'startmem'}/$mem)-1);
    }
    if($self->{'startload'}) {
	# load should be between 0-10ish
	# 0 load => 0
	no warnings 'numeric';
	my $load = $self->load_status();
	if($self->{'startload'} > 0) {
	    # Stop if the load is above the limit
	    $status += ::max(0,$load - $self->{'startload'});
	} else {
	    # Stop if the load is below the limit (for sensor)
	    $status += ::max(0,-$load - $self->{'startload'});
	}
    }
    if($self->{'startnoswap'}) {
	# swap should be between 0-10ish
	# swap in or swap out or no swap = 0
	# else log(swapin*swapout)
	my $swap = $self->swap_status();
	$status += log(::max(1, $swap - $self->{'startnoswap'}));
    }
    if($self->{'startio'}) {
	my $io = $self->io_status();
	$status += ::max(0,$io - $self->{'startio'});
    }
    $self->{'over_start_limit'} = $status;
    if(not $::opt_recheck) {
	$self->{'recheck'} = $self->{'factor'} * $self->{'over_start_limit'};
    }
    ::debug("over_start_limit: $status\n");
    return $self->{'over_start_limit'};
}


sub hard {
    my $self = shift;
    return $self->{'hard'};
}


sub verbose {
    my $self = shift;
    return $self->{'verbose'};
}


sub sleep_for_recheck {
    my $self = shift;
    if($self->{'recheck'} < 0.5) {
	# Never sleep less than 0.5 sec
	$self->{'recheck'} = 0.5;
    }
    if($self->verbose()) {
	$self->{'recheck'} = int($self->{'recheck'}*100)/100;
	print "Sleeping $self->{'recheck'}s\n";
    }
    ::debug("recheck in $self->{'recheck'}s\n");
    ::usleep(1); # For some reason this gets interrupted
    ::usleep(1000*$self->{'recheck'});
}


sub sleep_while_running {
    my $self = shift;
    ::debug("check in $self->{'runtime'}s\n");
    if($self->verbose()) {
	$self->{'runtime'} = int($self->{'runtime'}*100)/100;
	print "Running $self->{'runtime'}s\n";
    }
    ::usleep(1); # For some reason this gets interrupted
    ::usleep(1000*$self->{'runtime'});
}


sub nonblockGetLines {
    # An non-blocking filehandle read that returns an array of lines read
    # Returns:  ($eof,@lines)
    # Example: --sensor 'vmstat 1 | perl -ane '\''$|=1; 4..0 and print $F[8],"\n"'\'
    my ($fh,$timeout) = @_;

    $timeout = 0 unless defined $timeout;
    my $rfd = '';
    $::nonblockGetLines_last{$fh} = ''
        unless defined $::nonblockGetLines_last{$fh};

    vec($rfd,fileno($fh),1) = 1;
    return unless select($rfd, undef, undef, $timeout)>=0;
    # I'm not sure the following is necessary?
    return unless vec($rfd,fileno($fh),1);
    my $buf = '';
    my $n = sysread($fh,$buf,1024*1024);

    my $eof = eof($fh);
    # If we're done, make sure to send the last unfinished line
    return ($eof,$::nonblockGetLines_last{$fh}) unless $n;
    # Prepend the last unfinished line
    $buf = $::nonblockGetLines_last{$fh}.$buf;
    # And save any newly unfinished lines
    $::nonblockGetLines_last{$fh} =
        (substr($buf,-1) !~ /[\r\n]/ && $buf =~ s/([^\r\n]*)$//)
	? $1 : '';
    $buf ? ($eof,split(/\n/,$buf)) : ($eof);
}

sub read_sensor {
    my $self = shift;
    my $fh = $self->{'sensor_fh'};
    if(not $fh) {
	# Start the sensor
	open($fh, "-|", $::opt_sensor) || ::die_bug("Cannot open: $::opt_sensor");
	$self->{'sensor_fh'} = $fh;
    }
    # Read as much as we can (non_block)
    my ($eof,@lines) = nonblockGetLines($fh);
    
    # new load = last full line
    foreach my $line ( @lines ) {
	if(defined $line) {
	    print "Pipe saw: $eof [$line]\n";
	    $Global::last_sensor_reading = $line;
	}
    }
    if($eof) { undef($self->{'sensor_fh'}); }

    return $Global::last_sensor_reading;
}

sub load_status {
    # Returns:
    #   loadavg or sensor measurement
    my $self = shift;
    if($::opt_sensor) {
	if(not defined $self->{'load_status'} or
	   $self->{'load_status_cache_time'} + $self->{'recheck'} < time) {
	    $self->{'load_status'} = $self->read_sensor();
	    while (not defined $self->{'load_status'}) {
		sleep 1;
		$self->{'load_status'} = $self->read_sensor();
	    } 
	    $self->{'load_status_cache_time'} = time;
	}
    } else {
	# Normal load avg
	# Cache for some seconds
	if(not defined $self->{'load_status'} or
	   $self->{'load_status_cache_time'} + $self->{'recheck'} < time) {
	    $self->{'load_status'} = load_status_linux();
	    $self->{'load_status_cache_time'} = time;
	}
    }
    ::debug("load_status: ".$self->{'load_status'}."\n");
    return $self->{'load_status'};
}

sub undef_as_zero {
    my $a = shift;
    return $a ? $a : 0;
}


sub load_status_linux {
    my ($loadavg);
    if(open(IN,"/proc/loadavg")) {
	# Linux specific (but fast)
	my $upString = <IN>;
	if($upString =~ m/^(\d+\.\d+)/) {
	    $loadavg = $1;
	} else {
	    ::die_bug("proc_loadavg");
	}
	close IN;
    } elsif (open(IN,"uptime|")) {
	my $upString = <IN>;
	if($upString =~ m/averages?.\s*(\d+\.\d+)/) {
	    $loadavg = $1;
	} else {
	    ::die_bug("uptime");
	}	
	close IN;
    }
    return $loadavg;
}


sub swap_status {
    # Returns:
    #   (swap in)*(swap out) kb
    my $self = shift;
    # Cache for some seconds
    if(not defined $self->{'swap_status'} or
       $self->{'swap_status_cache_time'}+$self->{'recheck'} < time) {
	my $status = swap_status_linux();
	$self->{'swap_status'} = ::max($status,0);
	$self->{'swap_status_cache_time'} = time;
    }
    ::debug("swap_status: $self->{'swap_status'}\n");
    return $self->{'swap_status'};
}


sub swap_status_linux {
    my $swap_activity;
    $swap_activity = "vmstat 1 2 | tail -n1 | awk '{print \$7*\$8}'";
    # Run swap_activity measuring.
    return qx{ $swap_activity };
}


sub mem_status {
    # Returns:
    #   number of bytes (free+cache)
    my $self = shift;
    # Cache for one second
    if(not defined $self->{'mem_status'} or
       $self->{'mem_status_cache_time'}+$self->{'recheck'} < time) {
	$self->{'mem_status'} = mem_status_linux();
	$self->{'mem_status_cache_time'} = time;
    }
    ::debug("mem_status: $self->{'mem_status'}\n");
    return $self->{'mem_status'};
}


sub mem_status_linux {
    #              total       used       free     shared    buffers     cached
    # Mem:       3366496    2901664     464832          0     179228    1850692
    # -/+ buffers/cache:     871744    2494752
    # Swap:      6445476    1396860    5048616
    my @free = `free`;
    my $free = (split(/\s+/,$free[2]))[3];
    return $free*1024;
}


sub io_status {
    # Returns:
    #   max percent for all devices
    my $self = shift;
    # Cache for one second
    if(not defined $self->{'io_status'} or
       $self->{'io_status_cache_time'}+$self->{'recheck'} < time) {
	$self->{'io_status'} = io_status_linux();
	$self->{'io_status_cache_time'} = time;
    }
    ::debug("io_status: $self->{'io_status'}\n");
    return $self->{'io_status'};
}


sub io_status_linux {
    # Device: rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
    # sda       0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
    my @iostat_out = `LANG=C iostat -x 1 2`;
    # throw away all execpt the last Device:-section
    my @iostat;
    for(reverse @iostat_out) {
	/Device:/ and last;
	push @iostat, (split(/\s+/,$_))[13];
    }
    my $io = ::max(@iostat);
    return $io/10;
}

$::exitsignal = $::exitstatus = 0; # Dummy