#!/bin/bash

# +----------------------------------------------------------------------------+
# |                          Jeffrey M. Hunter                                 |
# |                      jhunter@idevelopment.info                             |
# |                         www.idevelopment.info                              |
# |----------------------------------------------------------------------------|
# |      Copyright (c) 1998-2012 Jeffrey M. Hunter. All rights reserved.       |
# |----------------------------------------------------------------------------|
# | DATABASE   : Oracle                                                        |
# | FILE       : hugepages_settings.sh                                         |
# | CLASS      : UNIX Shell Scripts                                            |
# | PURPOSE    : Linux BASH script used to compute recommended values for      |
# |              setting vm.nr_hugepages in a HugePages/HugeTLB configuration. |
# |                                                                            |
# |              This 
# |                                                                            |
# | PARAMETERS :                                                               |
# |              TARGET_DB_NAME       TNS connect string to the target         |
# |                                   database.                                |

# |                                   files to retain on the file system.      |
# |                                                                            |
# | EXAMPLE RUN:                                                               |
# |              hugepages_settings.sh
# |                                                                            |
# | CRON USAGE : This script can be run interactively from a command line      |
# |              interface or scheduled within CRON. Regardless of the method  |
# |              used to run this script, a log file will automatically be     |
# |              created of the form "<script_name>_<varn>.log" where <varn>   |
# |              can be any user defined variable used to identify the         |
# |              instance of the run. The location of this log file will be    |
# |              specified in the "DPUMP_LOG_DIR" parameter of this script     |
# |              (see above). When scheduling this script to be run from CRON, |
# |              ensure the crontab entry does NOT redirect its output to the  |
# |              name of the log file automatically created from within this   |
# |              script by Data Pump. When defining the crontab entry used to  |
# |              run this script, the typical convention is to redirect its    |
# |              output to a log file with an extension of .job as illustrated |
# |              in the following example:                                     |
# |                                                                            |
# |              [time] [script_name.ksh] > [script_name.job] 2>&1             |
# |                                                                            |
# | NOTE       : As with any code, ensure to test this script in a development |
# |              environment before attempting to run it in production.        |
# +----------------------------------------------------------------------------+

#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.
#


# Welcome text
echo "
This script is provided by Doc ID 401749.1 from My Oracle Support 
(http://support.oracle.com) where it is intended to compute values for 
the recommended HugePages/HugeTLB configuration for the current shared 
memory segments. Before proceeding with the execution please make sure 
that:
 * Oracle Database instance(s) are up and running
 * Oracle Database 11g Automatic Memory Management (AMM) is not setup 
   (See Doc ID 749851.1)
 * The shared memory segments can be listed by command:
     # ipcs -m

Press Enter to proceed..."

read

# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`

# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk '{print $2}'`

# Initialize the counter
NUM_PG=0

# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk '{print $5}' | grep "[0-9][0-9]*"`
do
   MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
   if [ $MIN_PG -gt 0 ]; then
      NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
   fi
done

RES_BYTES=`echo "$NUM_PG * $HPG_SZ * 1024" | bc -q`

# An SGA less than 100MB does not make sense
# Bail out if that is the case
if [ $RES_BYTES -lt 100000000 ]; then
   echo "***********"
   echo "** ERROR **"
   echo "***********"
   echo "Sorry! There are not enough total of shared memory segments allocated for 
HugePages configuration. HugePages can only be used for shared memory segments 
that you can list by command:

   # ipcs -m

of a size that can match an Oracle Database SGA. Please make sure that:
 * Oracle Database instance is up and running 
 * Oracle Database 11g Automatic Memory Management (AMM) is not configured"
   exit 1
fi

# Finish with results
case $KERN in
   '2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
          echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
   '2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    *) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac