MonitoringLinuxPerformancefortheSQLServerAdminAnthonyNocentino,EnterpriseArchitect,Centino Systems

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Career Centerhttp://www.pass.org/Careers.aspx

AnthonyE.NocentinoEnterpriseArchitect,CentinoSystems

aen@centinosystems.com

ConsultantandTrainer

FounderandPresidentofCentino Systems

Specializeinsystemarchitectureandperformance

ComputerScience,M.S.andB.S.

MicrosoftMVP- DataPlatform

FriendofRedgate

LinuxFoundationCertifiedEngineer

MicrosoftCertifiedProfessional

Otherplacesonline…

Blog- www.centinosystems.com/blog

PluralsightAuthor

/nocentino @nocentino

• LinuxSystemArchitecture• SQLonLinuxArchitecture• SystemComponents

• CPU/Processes• Memory/Pages• Disk/FileSystems

• MonitoringTools

Agenda

• LinuxOSconcepts,howitworks!• Toolstoviewperformancedata• What’sgoodandwhat’sbad

Thingswe’regoingtocover

Thingswe’reNOTgoingtocover• SQLServerinternals• Performancetroubleshooting

LinuxArchitecture

Kernel Resource Management and AccessProcess, Pages and File

Systems

ShellExecutes Your

Commands…Your Interface to the Kernel

Commands, Editors…any User Program

Hardware Physical Resources CPU, Memory and Disk

Users Interact with the Shell Cause Problems :)

Kern

el

Spac

eUs

er S

pace

SQLonLinuxArchitecture- Drawbridge

From:https://blogs.technet.microsoft.com/dataplatforminsider/2016/12/16/sql-server-on-linux-how-introduction/

SQLOS

PlacingtasksintoworkersandgettingaccesstotheCPU

Controllingaccesstosystemresources

SchedulingofI/Obothnetworkanddisk

Allocationofmemorytovarioussystemobjects

Scheduling Synchronization I/OMemoryManagement

PrimaryfunctionisresourcemanagementspecifictoRDBMS

“AnewplatformlayerinSQLServer2005toexploitnewhardwarecapabilitiesandtheirtrends”S.Oks

“OperatingSystemsupportforDatabaseManagement”M.Stonebraker

SQLonLinuxArchitecture- ProcessLayout

From: https://blogs.technet.microsoft.com/dataplatforminsider/2016/12/16/sql-server-on-linux-how-introduction/

SQLonLinuxArchitecture- SQLPAL

From:https://blogs.technet.microsoft.com/dataplatforminsider/2016/12/16/sql-server-on-linux-how-introduction/

AllotherCode

Win32HostedAPIs(LibOS) SQLOSAPI

SQLOSv2

HostExtension(Memory,Threads/Scheduling,I/O)

PerformanceSensitiveCode

LinuxKernelviaSystemCalls

• CalltablemapsWin32APIsemanticstoLinuxSystemcalls• ~45ABICalls• MemoryManagement• ThreadsandScheduling• SynchronizationPrimitives• I/ONetworkandDisk

• Wecarealotabouthostextensions…it’smorecode

SQLonLinuxArchitecture- HostExtensions

• Processvirtualization(notmachine)• Presentinganotherenvironmentinsidetheprocess’contextthat’sdifferentthan

thatofthehardware’soperatingenvironment

• ButtheenvironmentispurposebuiltforSQLServer

• WeneedtounderstandthatthisisahybridWin32/Linuxprocessandhaveafirmgraspof• ResourceallocationandmanagementinSQLPAL• HowthatturnsintoLinuxOSperformance• Debugging

Shhhhhh- SQLPALisVirtualization;)

CPUandProcesses

• Process• Executingprogram,programcode,memoryandresources

• Thread(LWP)• Sharedaccesstoresources

• ProcessandThreadCreation• fork/exec - parentprocessyieldsachildprocesswithanewPID• clone - sameaddressspaceasthreadcreator,cheapandfast!

• ProcessTree• Thehierarchyofparentandit’schildprocesses

WhatisaProcess

• Process States

WhatisaProcess(con’t)

Running

Runnable

ZombieStopped

Sleeping

• Signals• Methods of process control• kill and killall

• Niceness• Set the execution priority• nice and renice• Default 20, lower is less “nice”

ControllingProcesses

• Contextswitching• KernelversusUserMode• CPUScheduling• HowisaSQLOSWorkerscheduledontotheCPU?• Createsathreadviapthreadandthat’spushedintothescheduler

• pthreads?

MoreonProcesses…

• Unitofschedulingisthethread• DefaultschedulerisSCHED_OTHER/SCHED_NORMAL

• Timesharingscheduler• Preemptive• Dynamicprioritylist,basedonniceness• Calculatedquantumlengthbasedonpriority

Process/ThreadScheduling

• Unitofschedulingisthethread• DefaultschedulerisSCHED_OTHER/SCHED_NORMAL

• Timesharingscheduler• Preemptive• Dynamicprioritylist,basedonniceness• Calculatedquantumlengthbasedonpriority• kernel.sched_min_granularity_ns = 10000000 (10ms)- default• kernel.sched_wakeup_granularity_ns = 15000000 (15ms)- default

• NUMAAware,but…• kernel.numa_balancing = 0 - default

Process/ThreadScheduling

• Percentageofwhat?• Loadaverage• RunqueuelengthandI/Owaits• Spikesaren’tbad• Longwaits• User• I/O- disklatencywilleffectaccesstotheCPU• System

CPU- Whattolookfor?

• top/htop• ps• mpstat/pidstat• dstat• procfs

Toolstouseforprocessmonitoring

• Processesandthreads• RunloadaverageunderCPUsaturation• Exploringprocfs

Demos

MemoryandPages

• MemoryLayoutandArchitecture• PhysicalandVirtualMemory• NUMA- freelistspernode• Pages(Anonymous)• DemandPaging• Swapout• TimeandPressure

• Swapin,MajorPageFault• Allocation,MinorPageFault

• FileSystemCacheandswappiness - http://red.ht/2cHg9Vk

Memory

• Regularpages- 4KB• Transparenthugepages- 2MB• IncreasesmemoryI/ObydecreasingTLBcachemisses

• SQLOSv2• CanrequestlargepagesinsideSQLServer…withtraceflag834• SQLwillallocatememoryonstartup• WhenSQLPALexposes8GB+toSQLServer

• Asoftoday,nolockedpages…butTF835ison?

Pages

• Highconsumersofspace• Physical• Virtual

• ExternalmemorypressureonSQLServer• Excessiveswapping• swappingin/out

Memory- Whattolookfor?

• /proc/meminfo• free• top/htop• ps• vmstat• pidstat

Toolstouseformemorymonitoring

• Memorylayout• Isolatingamemoryhog• Identifyingexternalmemorypressure• ExternalmemorypressureonSQLServer

• Excessiveswapping• Swappingin/Swappingout

Demos

DisksandFileSystems

• Sectors(physical)• Actualstorageunitofthedisk,512Bor4KB

• Blocks(logical)• FundamentalunitofI/O,allocation

• Diskshavefiniteperformancecharacteristics• Bandwidth- howmuchdata• Latency- howfast

• StorageInterconnects• Internal• External

Disks

• XFS• Defaultfilesystem- http://red.ht/2dBXccx

• EXT4• Blocksize• Impactutilizationandperformancenominally• 4KBdefaultblocksize

• Mounttimeoptions• Accesstimes- noatime

FileSystems

• XFSandEXT4essentiallythesame• Files• i-nodes• Extents• Blocks

BlockAllocationinLinux

• StreamI/OviaNTUM

• FastI/Oviathehostextension• KernelasynchronousIO(kaio)• io_submit()• Returnstocallerimmediately,completionpollingisinuserspace

• O_DIRECT - bypassespagecacheandI/Ostaysinusermode• fsync()• “probablydesignedbyaderangedmonkeyonsomeseriousmind-controllingsubstances.”- Linus• man 2 open

I/OunderSQLPAL

• SaturateddisksandI/Osubsystems• Swapping• Baseline!

Disks- Whattolookfor?

• iostat• iotop• pidstat• dstat

Toolstousefordiskmonitoring

• FindinghighI/Oprocesses• Measuringdisklatency(DMVsandcmdlinetools)• sys.dm_io_virtual_file_stats

Demos

MonitoringTools

• Nearlyeverythingwe’vetalkedaboutsofarhasbeenpointintime…whataboutbaselining?

• sar - SystemActivityReporter• dstat - writestoCSV

BaseliningTools

• Youhaveallofthesametoolsyou’reusedtoforSQLServer• BecauseofSQLOSweget• DMVs• ExtendedEvents

ToolsforMonitoringSQLServer

• NewDMVs

• PSSDiag• https://blogs.msdn.microsoft.com/sqlcat/2017/08/11/collecting-performance-data-with-

pssdiag-for-sql-server-on-linux/• DBFS• https://github.com/Microsoft/dbfs• http://www.centinosystems.com/blog/sql/dbfs-command-line-access-to-sql-server-dmvs/

• Grafana• https://blogs.msdn.microsoft.com/sqlcat/2017/07/03/how-the-sqlcat-customer-lab-is-

monitoring-sql-on-linux/

NewToolsAvailableforSQLonLinux

• Don’tjustlistentome…here’swhatMicrosoftisinterestedin• CPU- mpstat,pidstat• Disk- iostat,iotop• Memory- free,sar• Network- sar• DMVData• Systemloginformation

MetricsCapturedbyPSSDiag

• LinuxSystemArchitecture• SQLonLinuxArchitecture• SystemComponents

• CPU/Processes• Memory/Pages• Disk/FileSystems

• MonitoringTools

Review

Needmoredata?Blogwww.centinosystems.com/blog

PluralsightUnderstandingandUsingEssentialToolsforEnterpriseLinux7Linuxbasics,systemarchitecture,fileanddirectorymanagement

LFCE:AdvancedNetworkandSystemAdministrationsystemd,PerformanceandTools,remotefilesystemsandKerberos

SQLServeronLinuxAdministrationFundamentalsInstallation,configurationandmanagement

References

Manyofthemanpages

https://docs.microsoft.com/en-us/sql/linux/sql-server-linux-performance-best-practices

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/performance_tuning_guide/index

https://www.kernel.org/doc/Documentation/

https://ext4.wiki.kernel.org/index.php/Clarifying_Direct_IO%27s_Semantics

Questions?

SQLServeronLinux:DBAFocusedLessonsLearnedfromEarlyDeployments• Denzil Ribeiro

Comingupnext….

Thankyouforattending!