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Oracle Hugepages Configuration¶

1. Disable transparent hugepages¶

Check current status about transparent hugepages

cat /sys/kernel/mm/transparent_hugepage/enabled

If result is never, you can skip this sop

Modify grub file and append transparent_hugepage=never

vim /etc/default/grub

Rebuild files

backup and rebuilding file

cp -rp /boot/efi/EFI/redhat/grub.cfg /boot/efi/EFI/redhat/grub.cfg.$(date +%Y.%m.%d)
grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
cat /boot/efi/EFI/redhat/grub.cfg | grep transparent_hugepage

Reboot the system, and check result after reboot

cat /sys/kernel/mm/transparent_hugepage/enabled

2. Setup memory lock for hugepages configuration¶

Setup memory lock

vim /etc/security/limits.conf

example : 512G(base on your total physical memory) * 1024 * 1024 * 0.9 = 483183820

*    soft memlock 483183820
*    hard memlock 483183820

Check memory lock in /etc/security/limits.conf

3. Calculate the recommended value for the parameter of `vm.nr_hugepages`¶

Prepare script

vim /home/oracle/hugepages_setting.sh

add below 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 the overall 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 $KERN in
    '2.4') HUGETLB_POOL=`echo "$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" ;;
    '4.14') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    '4.18') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    '5.4') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    *) echo "Kernel version $KERN is not supported by this script (yet). Exiting." ;;
esac

# End

Execute by oracle (make sure all DBs are opened on the server)

chmod 755 /home/oracle/hugepages_setting.sh
sh /home/oracle/hugepages_setting.sh

Add parameter file in /etc/sysctl.conf

If you change this value, you must reboot OS!! (switch to root account)

vim /etc/sysctl.conf

add → vm.nr_hugepages = 12804 < --- base on the value from step 3.2

shutdown all DBs and reboot OS

4. Check the hugepages configuration¶

Check in OS

grep HugePages /proc/meminfo

before start DB

after start DB

Check all DB alert log

cat /oracle/diag/rdbms/wzsdw/WZSDW/trace/alert_WZSDW.log