#!/usr/bin/perl -wT
#
# ctrl_athcool.pl
# Version: 1.0.0 05-JUL-2007
# Author:  David Mathog, Biology Division, Caltech
# Contact: mathog@caltech.edu
# Copyright: 2007, David Mathog and Caltech
#
# This procedure keeps on eye on how busy the system is and
# toggles athcool on or off.  If the system is busy, it turns it
# off, and if it is slow it turns it on.  This enables power saving
# on a more or less idle system, without sacrificing (much) performance when
# the system is busy.
#
# It looks ONLY at the idle time in /proc/stat.  The higher that value per
# second the more idle the system is, the lower that value per second, the more
# busy the system is.  Start this as a daemon when athcool starts.
#
# 
#
# Parameters are:
#   None, values are hardwired in here
#
#####################################################################
# License terms:
#
# 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 2
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
####################################################################

use strict;
####################################################################
# site specific values, modify to fit your site!!!!
#
delete @ENV{'ENV', 'BASH_ENV'};  #or -T complains
$ENV{PATH}        = '/bin:/usr/bin:/usr/local/bin';
my $STATFILE      = '/proc/stat';
my $ATHCOOL       = '/usr/sbin/athcool';
my $INTERVAL      = 1;  # time sampling interval in seconds
my $THRESH_DOWN   = 50; # threshold for idle measurement going down (indicates a busy system)
my $THRESH_UP     = 70; # threshold for idle measurement going up   (indicates an idle system) 
my $DELAY_OFF     = 1;  # seconds it must busy (below THRESH_DOWN) before athcool off
my $DELAY_ON      = 3;  # seconds it must idle (above THRESH_UP)   before athcool on
####################################################################
#
# Do not modify anything below this point
#
my $lastidle=0;     #idle time info from last interval
my $idle;           #idle time info from this interval
my $idif;
my $line;
my @chunks;
my $discard_text;
my $count_down = $DELAY_OFF;
my $count_up   = $DELAY_ON;

# start athcool (script must know what state athcool is in, harmless if athcool is already running)
my $athcool_state = 1; 
$discard_text= `$ATHCOOL on`;
while (1) {
   open (SFILE, "<$STATFILE") or die;
   $line = <SFILE>;
   close(SFILE);
   @chunks = split(" ",$line); 
                        #0 is "CPU" string
   $idle  = $chunks[4];  #Time in idle state
   if($lastidle == 0){
     $lastidle = $idle;  # and don't shift anything
   }
   else {
     $idif = $idle - $lastidle;  # fraction of time idle 0 to 100 (more or less)
     $lastidle = $idle;
     if($idif >= $THRESH_UP){
       $count_up   -= 1;
       $count_down  = $DELAY_OFF;
       if($count_up <= 0){
         $count_up= 0;
         if($athcool_state == 0){
           $discard_text= `$ATHCOOL on`;
           $athcool_state = 1;
         }
       }
     }
     elsif($idif <= $THRESH_DOWN){
       $count_up    = $DELAY_ON;
       $count_down -= 1;
       if($count_down <= 0){
         $count_down = 0;
         if($athcool_state == 1){
           $discard_text= `$ATHCOOL off`;
           $athcool_state = 0;
         }
       }
     }
     else {
       $count_up   = $DELAY_ON;
       $count_down = $DELAY_OFF;
     }
   }
   sleep(1);
}
exit;