Complete steps to quickly configure HugePages under Linux systems

preface

Regarding the OPTIMIZATION of HugePages and Oracle database of Linux system, you can refer to the previous articles of Xiong Ye, and the related concepts are very clear:

Linux large memory page Oracle database optimization

This article aims to quickly configure HugePages on Linux systems

Test environment: RHEL6.8 + 512G physical memory; Oracle 11.2.0.4 SGA G = 400.

1. Set memlock unlimited

In/etc security/limits conf configuration file, set oracle memlock unlimited user:

vi /etc/security/limits.conf

oracle soft memlock unlimited
oracle hard memlock unlimited

2. Set vm.nr_ES44en reasonably

In the /etc/ sysctl.conf configuration file, set the reasonable value of vm.es52EN_ES53en.

Run the hugepages_settings.sh script provided by MOS 401749.1 to get the recommended value directly.

hugepages_settings. sh Script content:

#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
# on Oracle Linux
#
# 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.
#
# This script is provided by Doc ID 401749.1 from My Oracle Support 
# http://support.oracle.com

# 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 on Oracle Linux. Before proceeding with the execution please note following:
* For ASM instance, it needs to configure ASMM instead of AMM.
* The 'pga_aggregate_target' is outside the SGA and 
you should accommodate this while calculating SGA size.
* In case you changes the DB SGA size, 
as the new SGA will not fit in the previous HugePages configuration, 
it had better disable the whole HugePages, 
start the DB with new SGA size and run the script again.
And 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 $2}'`
if [ -z "$HPG_SZ" ];then
echo "The hugepages may not be supported in the system where the script is being executed."
exit 1
fi

# Initialize the counter
NUM_PG=0

# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | cut -c44-300 | awk '{print $1}' | grep "[0-9][0-9]*"`
do
MIN_PG=`echo "$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
'2.2') echo "Kernel version $KERN is not supported. Exiting." ;;
'2.4') HUGETLB_POOL=`echo "$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" ;;
'3.8') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
'3.10') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
'4.1') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
esac

# End

Run the script directly to get the corresponding suggestions:

-- When starting the instance Settings SGA_MAX_SIZE=12G , give advice: 
Recommended setting: vm.nr_hugepages = 6148

-- When starting the instance Settings SGA_MAX_SIZE=400G , give advice: 
Recommended setting: vm.nr_hugepages = 204805

-- When no instance is started, an error message is sent: 
***********
** ERROR **
***********
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

Here I append the suggested value vm.nr_hugepages = 204805 to the /etc/ sysctl.conf configuration file and then execute the sysctl-ES80en active configuration.

3. Confirm that the HugePages setting is successful

To view the information about HugePages, note that the value of HugePages_Total is set to 204805:

grep Huge /proc/meminfo

# grep Huge /proc/meminfo 
AnonHugePages: 0 kB
HugePages_Total: 204805
HugePages_Free: 168475
HugePages_Rsvd: 168471
HugePages_Surp: 0
Hugepagesize: 2048 kB

When the database is started, there will be "Large Pages Information" in the corresponding alert log:

Wed Nov 14 14:38:12 2018
Starting ORACLE instance (normal)
************************ Large Pages Information *******************
Per process system memlock (soft) limit = UNLIMITED

Total Shared Global Region in Large Pages = 400 GB (100%)

Large Pages used by this instance: 204801 (400 GB)
Large Pages unused system wide = 4 (8192 KB)
Large Pages configured system wide = 204805 (400 GB)
Large Page size = 2048 KB
********************************************************************

At this point, you can confirm that the HugePages setting was successful.

conclusion