為Linux版本Oracle 11gR2配置HugePage

531968912發表於2016-05-18

 

HugePageOracleLinux版本下一種效能最佳化手段。對於共享記憶體區域(SGA)的資料庫系統,Oracle通常都推薦在作業系統層面配置上HugePage,為Oracle例項準備更大的可用共享記憶體和整塊的記憶體。

 

本文主要介紹在Oracle 11gR2版本上,進行HugePage配置全過程。記錄下來,共需要的朋友待查。

 

1、環境介紹

 

筆者使用Oracle 11gR2系統,具體版本為11.2.0.4

 

 

SQL> select * from v$version;

 

BANNER

--------------------------------------------------------------------------------

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

PL/SQL Release 11.2.0.4.0 - Production

CORE     11.2.0.4.0     Production

TNS for Linux: Version 11.2.0.4.0 - Production

NLSRTL Version 11.2.0.4.0 – Production

 

 

當前資料庫配置記憶體策略為ASMM,也就是分別設定PGASGA的大小範圍。Oracle根據負載情況動態自己調節內部各個子池的空間。注意:在當前版本中,AMMAutomatic Memory Management)和HugePage之間還是不能相容。所以,如果要求配置HugePage,就只能退而求其次選擇ASMM

 

資料庫設定的SGA空間如下:

 

 

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 12G

sga_target                           big integer 12G

 

 

12GSGAOracle在啟動過程中,針對大記憶體情況給出了提示在alert log中。

 

ue Jan 12 11:31:33 2016

Starting ORACLE instance (normal)

************************ Large Pages Information *******************

Per process system memlock (soft) limit = 64 KB

 

Total Shared Global Region in Large Pages = 0 KB (0%)

 

Large Pages used by this instance: 0 (0 KB)

Large Pages unused system wide = 0 (0 KB)

Large Pages configured system wide = 0 (0 KB)

Large Page size = 2048 KB

 

RECOMMENDATION:

  Total System Global Area size is 12 GB. For optimal performance,

  prior to the next instance restart:

  1. Increase the number of unused large pages by

 at least 6145 (page size 2048 KB, total size 12 GB) system wide to

  get 100% of the System Global Area allocated with large pages

  2. Large pages are automatically locked into physical memory.

 Increase the per process memlock (soft) limit to at least 12 GB to lock

 100% System Global Area's large pages into physical memory

 

 

首先Oracle發現當前系統並沒有設定HugePage,只有預設的2M大小的Page可選。於是,從建議的角度,給出了提示意見,建議開啟HugePage選項在作業系統層面。此時,作業系統層面也沒有專門的設定。

 

 

[oracle@PROD_PC-DB trace]$ grep Huge /proc/meminfo

AnonHugePages:     36864 kB

HugePages_Total:       0

HugePages_Free:        0

HugePages_Rsvd:        0

HugePages_Surp:        0

Hugepagesize:       2048 kB

 

 

2、配置HugePage

 

11.2的小版本中,HugePage處理的行為其實是在變化的。在11.2.0.2中,Oracle推出了一個引數use_large_page,作為從例項層面控制Oracle使用Huge Page的開關。

 

 

SQL> show parameter large_pages

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

use_large_pages                      string      TRUE

 

 

該引數預設取值為true,是一種向上最優策略。如果設定為trueOracle例項會去檢查是否作業系統開啟了HugePage,如果有就採用,如果沒有就不用。另外兩個取值分別為falseonly,如果選擇為false,表示Oracle例項不管作業系統設定,都不會使用HugePage。如果選擇為only,就表示Oracle例項只會選擇HugePage上執行。

 

此外,在行為上也有一些變化。在11.2.0.2版本中,如果作業系統沒有足夠的HugePage使用,SGA記憶體就只有使用系統剩下的小頁(Small Pages)。如果餘下的小頁small page不夠用,或者核心使用的比較多,系統會報錯ora-4030錯誤。

 

這個情況在11.2.0.3版本中有一些變化。Oracle首先會使用可用的HugePage,如果使用盡了,同樣會採用剩下的small pages作為SGA使用。變化在於對使用HugePage的方式上,根據官方的說法:

 

 

With this new behavior additional shared memory segments are an expected side effect. Part of the change is to ensure that each shared memory segment making up the SGA only contains sub-areas with an identical alignment requirement - hence the SGA will spread over more separate SHM segments. In this supported mixed page mode the database will exhaust the available hugepages, before switching to regular sized pages.

 

 

新版本的操作方式可以更好的使用可用的大頁資源。當前作業系統版本為Linux 2.6核心版本。

 

 

[oracle@PROD_PC-DB trace]$ uname -r

2.6.32-431.el6.x86_64

 

 

這個過程中涉及到不同作業系統環境、不同Oracle配置下的推薦HugePage數量問題。OracleMOS上釋出出一個Shell指令碼hugepages_settings.sh,可以動態計算出推薦的HugePage數量。

 

具體指令碼內容可以從MOS Doc ID 401749.1上進行下載,在筆者之前關於HugePage的文章中也有所涉及。執行指令碼後結果如下:

 

 

[oracle@PROD_PC-DB trace]$ ls -l | grep hugepag

-rw-r--r--. 1 oracle oinstall    3129 Jan 12 13:32 hugepages_settings.sh

[oracle@PROD_PC-DB trace]$ chmod +x hugepages_settings.sh

[oracle@PROD_PC-DB trace]$ ls -l | grep hugepag

-rwxr-xr-x. 1 oracle oinstall    3129 Jan 12 13:32 hugepages_settings.sh

 

 

[oracle@PROD_PC-DB trace]$ uname -r

2.6.32-431.el6.x86_64

 

[oracle@PROD_PC-DB trace]$ ./hugepages_settings.sh

 

This script is provided by Doc ID 401749.1 from My Oracle Support

() 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...

 

Recommended setting: vm.nr_hugepages = 6148

 

 

作業系統層面配置HugePage,需要在兩個層面進行配置。事先是limits.conf檔案,開啟對使用者的記憶體限制。

 

 

[root@PROD_PC-DB security]# vi limits.conf

 

# /etc/security/limits.conf

#

#Each line describes a limit for a user in the form:

#

(篇幅原因,有省略……

oracle soft nproc 2047

oracle hard nproc 16384

oracle soft nofile 1024

oracle hard nofile 65536

 

oracle soft memlock 32879476  --對應記憶體總量

oracle hard memlock 32879476

 

 

確認修改。

 

 

[oracle@PROD_PC-DB ~]$ ulimit -l

32879476

 

 

將指令碼計算出的結果,修改入/etc/sysctl.conf檔案。

 

 

net.ipv4.ip_local_port_range = 9000 65500

 

net.core.rmem_default = 262144

net.core.rmem_max = 4194304

net.core.wmem_default = 262144

net.core.wmem_max = 1048576

 

fs.aio-max-nr = 1048576

 

fs.file-max = 6815744

 

vm.nr_hugepages = 6148

"/etc/sysctl.conf" 67L, 1631C written

 

 

執行sysctl –p落實修改。

 

 

[root@PROD_PC-DB security]# sysctl -p

net.ipv4.ip_forward = 0

net.ipv4.conf.default.rp_filter = 1

(篇幅原因,有省略……

fs.file-max = 6815744

vm.nr_hugepages = 6148

 

 

重新啟動例項資料庫。

 

 

SQL> conn / as sysdba

Connected.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

 

Total System Global Area 1.2827E+10 bytes

Fixed Size                  2265224 bytes

Variable Size            2214596472 bytes

Database Buffers         1.0603E+10 bytes

Redo Buffers                7307264 bytes

Database mounted.

Database opened.

SQL>

 

 

在作業系統層面上,可以看到HugePage使用情況。

 

 

[oracle@PROD_PC-DB ~]$ ipcs -m

 

------ Shared Memory Segments --------

key        shmid      owner      perms      bytes      nattch     status     

0x00000000 786435     oracle     640        67108864   22                     

0x00000000 819204     oracle     640        12817793024 22                     

0x617ab988 851973     oracle     640        2097152    22                     

 

[oracle@PROD_PC-DB ~]$ grep Huge /proc/meminfo

AnonHugePages:     20480 kB

HugePages_Total:    6148

HugePages_Free:     5531

HugePages_Rsvd:     5528

HugePages_Surp:        0

Hugepagesize:       2048 kB

 

 

同時,啟動過程中的推薦提示資訊消失。

 

 

Tue Jan 12 14:26:30 2016

Starting ORACLE instance (normal)

************************ Large Pages Information *******************

Per process system memlock (soft) limit = 31 GB

 

Total Shared Global Region in Large Pages = 12 GB (100%)

 

Large Pages used by this instance: 6145 (12 GB)

Large Pages unused system wide = 3 (6144 KB)

Large Pages configured system wide = 6148 (12 GB)

Large Page size = 2048 KB

********************************************************************

LICENSE_MAX_SESSION = 0

LICENSE_SESSIONS_WARNING = 0

Initial number of CPU is 8

Number of processor cores in the system is 8

Number of processor sockets in the system is 1

Picked latch-free SCN scheme 3

Using LOG_ARCHIVE_DEST_1 parameter default value as USE_DB_RECOVERY_FILE_DEST

Autotune of undo retention is turned on.

IMODE=BR

 

 

3、結論

 

對於投產在Linux版本下的Oracle共享記憶體系統而言,配置HugePage還是有現實意義的。


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