#!/usr/local/bin/perl -sT -w
use strict;
use POSIX;

#################################################################
#
# Geek    : smellysocks
# Contact : via www.perlmonks.com. my ID is smellysocks
#               http://www.perlmonks.com/index.pl?node_id=275665
# Purpose : Find out how to get a process to die gracefully when
#               it believes it may run out of memory...
# Notes   : This should prob be a module...
#
#           I tried to use an exit and was forced to use POSIX:_exit
#               routine instead. Do a "perldoc -f exit" to see why.
#               pay particular attention to this section:
#               "The exit() function does not always exit immediately"
#               It was news to me! 
# Bugs    : No bugs, they are all intentional features!
#           Assumtion that everything is a-ok at startup and
#               prior to first memory check.
#
#################################################################
#
# Functions/Subroutines:
#       memusage($PID)  : Return how much memory is in use by $PID 
#       memavail();     : Return how much mem is available


$ENV{PATH}="/usr/bin:/usr/sbin:/usr/local/bin:/usr/ccs/bin:/usr/openwin/bin:/usr/local/sbin";

# yeah, yeah, yeah. I could have typed in 2^20, etc., etc. etc
#   this is here to make everyone's life easier.
my $OneMB=1048576;
my $OneGig=1073741824;

# CHANGE ME FOR YOUR ENVIRONMENT!!!!
my $TOTALMEM=(2 * $OneGig );
#my $PERCENT_MAX=80;
my $PERCENT_MAX=50;
my $PID=$$;

############################################################
# Global Stuff 
my @MEMHOG;
my $PMAP="/usr/proc/bin/pmap";

# Assume everything is peachy before these are set.
my $PERCENT_USED=0;
my $PERCENT_AVAIL=100;
my $LASTMEMUSAGE=0;
my $loopcount=0;

#####################################################################

sub memusage {
   my ($PID)=@_;
   my $MEMUSAGE=0;

   open ( PMAP,"$PMAP $PID|") || return $MEMUSAGE; 
   while ( <PMAP> ) {
      next unless ( /^\s+total\s+(\d+)K.*$/ );
      $MEMUSAGE=+($1 * 1024);
   } # end of while <PMAP>

   close PMAP;
   return $MEMUSAGE;
} # end of memusage;

#####################################################################

sub memavail {
    # lose some time here.... :-( better way then vmstat?
    open ( VMSTAT,"vmstat 1 2|" ) || return -1;
    my @vmstat=(<VMSTAT>);
    close VMSTAT;
    @vmstat=split /\s+/,$vmstat[3];
    return ( $vmstat[4] * 1024 );
} # end of memavail

############################################################
#
#               Main Stuff/ Start Working
#
############################################################

print "I am pid: $PID. I'll be running $PMAP $PID many times\n";

open(LARGEFILE,"/kernel/genunix") || die "Unable to open $!";
my @LARGEFILE=(<LARGEFILE>);
close LARGEFILE;

# Magnify size of largefile 
for ( my $i=0; $i < 3; $i++ ) {         push @LARGEFILE,@LARGEFILE; }

while ( 1 ) {
   $loopcount++;
   my $MEMUSAGE=memusage $PID;

   # usage of pmap is mutually exclusive (one 1 process at a time)
   #    Protect/helps against multiple pmaps steping on each other.
   if ( $MEMUSAGE == 0 ) { $MEMUSAGE= $LASTMEMUSAGE; }

   # Print and do expensive work only every N lines/loopcount
   if ( ! ( $loopcount % 10  ) ) {
      my $AVAILMEM=memavail;    # lose a few seconds here...
      $PERCENT_USED=(  ( $MEMUSAGE / $TOTALMEM ) * 100 );
      $PERCENT_AVAIL=( ( $AVAILMEM / $TOTALMEM ) * 100 );
 
      # I hate line wraps...
      my $TIME=localtime(time());               # yuk. ugly temp var
      printf "The Time is: %s\n", $TIME;
      printf "Mem Used: %s  Percent Used: %3d%%  Percent Left: %3d%%",
              $MEMUSAGE,$PERCENT_USED,$PERCENT_AVAIL;
      printf "  cnt: %s\n\n", $loopcount;

      if ( $PERCENT_AVAIL <  ( 100 - $PERCENT_MAX ) ) {
         print "-=" x 30, "\n";
         print "The Hog has eaten everything in sight. ";
         print "Time for the slaughter.\n";
         print "-=" x 30, "\n";
         POSIX:_exit(1);
      }
   }

   # grab some memory -> should have found a better way to do this.
   push @MEMHOG,@LARGEFILE;
}

# Sample PMAP output:
#FF1D0000      8K read/write/exec     [ anon ]
#FF1E0000     16K read/exec         /usr/lib/libmp.so.2
#FF1F4000      8K read/write/exec   /usr/lib/libmp.so.2
#FF200000    984K read/exec         /usr/local/....
# ...
# total      816K