HugePage

HugePage 내용


주의

  1. SGA가 최소 16GB 이상 구성될 때 권장 (물리 메모리가 적다면 문제가 발생할 가능성이 큼)
  2. DB 인스턴스가 갑작스럽게 종료된 경우 HugePage에서 가지고 있던 메모리가 반환되기까지 시간이 걸리기 때문에 종료 직후 기동 시에 메모리 부족으로 인스턴스 기동이 되지 않을 수 있음


구성 방법

  1. AMM을 사용하고 있는지 확인. 사용 중이라면 HugePage 구성 불가능 
     SHOW PARAMETER MEMORY_TARGET;
 /*
 NAME          TYPE        VALUE 
 ------------- ----------- ----- 
 memory_target big integer 0 
 */
  2. 이하의 스크립트 실행 
     #!/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

    401749.1

  3. 스크립트 실행 결과 확인 ```sh 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…

    Recommended setting: vm.nr_hugepages = XXX ```

  4. 권장 값으로 HugePages 변경 
     sysctl -w vm.nr_hugepages=XXX

 # 재기동 이후에도 적용될 수 있도록 함
 vi /etc/sysctl.conf

 # 추가할 내용
 vm.nr_hugepages=XXX

  5. THP 비활성화

  6. USE_LARGE_PAGES 파라미터 값 변경 후 재기동 
     SHOW PARAMETER use_large_pages;
 /*
 NAME            TYPE   VALUE 
 --------------- ------ ----- 
 use_large_pages string FALSE
 */

 ALTER SYSTEM SET use_large_pages=ONLY SCOPE=SPFILE;
  7. HugePage 사용량 확인법 
     grep Huge /proc/meminfo

 #AnonHugePages:         0 kB
 #ShmemHugePages:        0 kB
 #HugePages_Total:       XXX
 #HugePages_Free:        0
 #HugePages_Rsvd:        0
 #HugePages_Surp:        0
 #Hugepagesize:       2048 kB


RDS에서의 HugePages


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