Linux系统下快速配置HugePages的完整步骤
前言
关于Linux系统的HugePages与Oracle数据库优化，可以参考熊爷之前的文章，相关概念介绍的非常清晰：
Linux大内存页Oracle数据库优化
本文旨在Linux系统上快速配置HugePages
测试环境：RHEL6.8+512G物理内存；Oracle11.2.0.4SGA=400G.
1.设置memlock无限制
在/etc/security/limits.conf配置文件中，设置oracle用户memlock无限制：
vi/etc/security/limits.conf
oraclesoftmemlockunlimited oraclehardmemlockunlimited
2.设置合理的vm.nr_hugepages
在/etc/sysctl.conf配置文件中，设置合理的vm.nr_hugepages值。
运行MOS401749.1提供的hugepages_settings.sh脚本，直接可以得到建议值。
hugepages_settings.sh脚本内容：
#!/bin/bash
#
#hugepages_settings.sh
#
#Linuxbashscripttocomputevaluesforthe
#recommendedHugePages/HugeTLBconfiguration
#onOracleLinux
#
#Note:Thisscriptdoescalculationforallsharedmemory
#segmentsavailablewhenthescriptisrun,nomatterit
#isanOracleRDBMSsharedmemorysegmentornot.
#
#ThisscriptisprovidedbyDocID401749.1fromMyOracleSupport
#http://support.oracle.com
#Welcometext
echo"
ThisscriptisprovidedbyDocID401749.1fromMyOracleSupport
(http://support.oracle.com)whereitisintendedtocomputevaluesfor
therecommendedHugePages/HugeTLBconfigurationforthecurrentshared
memorysegmentsonOracleLinux.Beforeproceedingwiththeexecutionpleasenotefollowing:
*ForASMinstance,itneedstoconfigureASMMinsteadofAMM.
*The'pga_aggregate_target'isoutsidetheSGAand
youshouldaccommodatethiswhilecalculatingSGAsize.
*IncaseyouchangestheDBSGAsize,
asthenewSGAwillnotfitinthepreviousHugePagesconfiguration,
ithadbetterdisablethewholeHugePages,
starttheDBwithnewSGAsizeandrunthescriptagain.
Andmakesurethat:
*OracleDatabaseinstance(s)areupandrunning
*OracleDatabase11gAutomaticMemoryManagement(AMM)isnotsetup
(SeeDocID749851.1)
*Thesharedmemorysegmentscanbelistedbycommand:
#ipcs-m
PressEntertoproceed..."
read
#Checkforthekernelversion
KERN=`uname-r|awk-F.'{printf("%d.%d\n",$1,$2);}'`
#FindouttheHugePagesize
HPG_SZ=`grepHugepagesize/proc/meminfo|awk'{print$2}'`
if[-z"$HPG_SZ"];then
echo"Thehugepagesmaynotbesupportedinthesystemwherethescriptisbeingexecuted."
exit1
fi
#Initializethecounter
NUM_PG=0
#Cumulativenumberofpagesrequiredtohandletherunningsharedmemorysegments
forSEG_BYTESin`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-gt0];then
NUM_PG=`echo"$NUM_PG+$MIN_PG+1"|bc-q`
fi
done
RES_BYTES=`echo"$NUM_PG*$HPG_SZ*1024"|bc-q`
#AnSGAlessthan100MBdoesnotmakesense
#Bailoutifthatisthecase
if[$RES_BYTES-lt100000000];then
echo"***********"
echo"**ERROR**"
echo"***********"
echo"Sorry!Therearenotenoughtotalofsharedmemorysegmentsallocatedfor
HugePagesconfiguration.HugePagescanonlybeusedforsharedmemorysegments
thatyoucanlistbycommand:
#ipcs-m
ofasizethatcanmatchanOracleDatabaseSGA.Pleasemakesurethat:
*OracleDatabaseinstanceisupandrunning
*OracleDatabase11gAutomaticMemoryManagement(AMM)isnotconfigured"
exit1
fi
#Finishwithresults
case$KERNin
'2.2')echo"Kernelversion$KERNisnotsupported.Exiting.";;
'2.4')HUGETLB_POOL=`echo"$NUM_PG*$HPG_SZ/1024"|bc-q`;
echo"Recommendedsetting:vm.hugetlb_pool=$HUGETLB_POOL";;
'2.6')echo"Recommendedsetting:vm.nr_hugepages=$NUM_PG";;
'3.8')echo"Recommendedsetting:vm.nr_hugepages=$NUM_PG";;
'3.10')echo"Recommendedsetting:vm.nr_hugepages=$NUM_PG";;
'4.1')echo"Recommendedsetting:vm.nr_hugepages=$NUM_PG";;
esac
#End
直接运行脚本即可得到对应的建议：
--当启动的实例设置SGA_MAX_SIZE=12G，给出建议： Recommendedsetting:vm.nr_hugepages=6148 --当启动的实例设置SGA_MAX_SIZE=400G，给出建议： Recommendedsetting:vm.nr_hugepages=204805 --当没有启动实例时，会报错提示： *********** **ERROR** *********** Sorry!Therearenotenoughtotalofsharedmemorysegmentsallocatedfor HugePagesconfiguration.HugePagescanonlybeusedforsharedmemorysegments thatyoucanlistbycommand: #ipcs-m ofasizethatcanmatchanOracleDatabaseSGA.Pleasemakesurethat: *OracleDatabaseinstanceisupandrunning *OracleDatabase11gAutomaticMemoryManagement(AMM)isnotconfigured
我这里将建议值vm.nr_hugepages=204805追加到/etc/sysctl.conf配置文件中，然后执行sysctl-p生效配置。
3.确认HugePages设置成功
查看关于HugePages的信息，注意HugePages_Total值是之前设置的204805：
grepHuge/proc/meminfo
#grepHuge/proc/meminfo AnonHugePages:0kB HugePages_Total:204805 HugePages_Free:168475 HugePages_Rsvd:168471 HugePages_Surp:0 Hugepagesize:2048kB
数据库在启动时，对应alert日志中会有“LargePagesInformation”内容：
WedNov1414:38:122018 StartingORACLEinstance(normal) ************************LargePagesInformation******************* Perprocesssystemmemlock(soft)limit=UNLIMITED TotalSharedGlobalRegioninLargePages=400GB(100%) LargePagesusedbythisinstance:204801(400GB) LargePagesunusedsystemwide=4(8192KB) LargePagesconfiguredsystemwide=204805(400GB) LargePagesize=2048KB ********************************************************************
至此可以确认HugePages设置成功。
总结
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