Improving System Performance by Creating Efficient Background Activities

Vikram SinghProgram Manager IIMicrosoft Corporation

Objectives

Help developers understand the importance of designing efficient background activity Provide developers with information and tools on efficient background activity designs

Agenda

IntroductionBackground activity impactChoosing the right modelWindows® 7 trigger-start servicesTask scheduler conditions and triggersSecurity and performance recommendationsCall to actionResources

Background Activity Primer

System activities that are not directly initiated by the user

Service, scheduled task, some COM processes (such as a COM service), WMI provider, and so on

Part of nearly every usage scenarioSearch indexingSystem security and maintenanceNetwork managementDevice managementSystem configuration

Performance• Less responsive to the user• Consumes resources from

foreground applications• Impacts boot, shutdown,

and logoff

Reliability• Memory leaks• System crashes, hangs• Dependent application

crashes

Security• An activity can require

system privileges • A successful attack can

compromise the entire system

Power Consumption

• Extra disk, CPU utilization• Decrease in battery life• Prevents idle efficiencies

Impact of Background Activity

Resource QuantityFile I/O 47,286

Copy-on-write (COW) pages 4,656 (~18MB)

Memory pages (Total) 15,967 (~60MB)

Registry operations 38,508

Threads 367

Case Study on Impact of Background Activity

Reviewed 49 Windows servicesThese services are not critical for boot and logonThey are critical and required for their individual features

Clean IT0

20

40

24.746.1

Boot Timeseconds

Clean IT0

153045

25.6 30

Shutdown Timeseconds

Clean IT0%

4%

8%

1.01%6.04%

Idle CPU Utilization15-second trace

Clean IT0

20,000

40,000

10,192 31,401

Disk Read Count15-second trace

Impact on Performance

Comparison of a clean Windows Vista® installation to an IT image that included 10 third-party services

Designing for Efficiency

Choose the right modelWindows service or scheduled task?

Leverage the latest Windows infrastructureTrigger-start services in Windows 7

Optimize performanceEliminate unnecessary privilegesEvaluate and measureIterate on optimizations

Win

dow

s S

ervi

ce • Continuous activity from boot to shutdown

• SCM (Service Control Manager) programming model

• Can specify dependency

Sch

edul

ed T

ask

• Short duration action

• Idle activity• Take action

on user logon• Standalone

executable or out-of-process COM server

• Generally execute

during a user session

Choosing the Right Model

Windows Services: Auto_Start

Auto_Start start type enables the service to launch at bootThis is the most commonly used service start type

Easy for developers because service is always running

ProblemsStartup time adds to boot timeAdds to system base footprintMany Auto_Start services wait for rare events

Windows Services: Trigger-Start

Windows 7 trigger-start services centralize environmental detection logic

SCM registers for interesting system eventsDevice arrivalIP address availabilityJoin or leave domainGroup policy updateFirewall port open or closeCustom Event Tracing for Windows (ETW) events

SCM starts or stops registered services based on events

Converting a Service to Trigger-Start

demo

Service Name Service Purpose Trigger Type

AELookupSvcProcesses application compatibility cache requests for applications as they are launched

Custom ETW

BDESVC Provides BitLocker client services for user interface and auto-unlocking of data volumes Custom ETW

BTHSERV Supports discovery and association of remote Bluetooth devices Device

SensorsMTPMonitorMonitors MTP (Media Transfer Protocol) sensors, such as a cell phone with a GPS receiver, to communicate sensor data to programs

Device

TabletInputService Enables pen and ink functionality Device

WinDefend Protects against spyware and potentially unwanted software Group Policy

Example of Trigger-Start Services

Service Shutdown – Best Practices

Service should self-stop immediately or after pre-determined idle time when task is completedOn system shutdown

Do not set SERVICE_ACCEPT_SHUTDOWN unless requiredNo need to free memory if the service is in a standalone processTarget less than 200ms for completing shutdown notification

Service Control Handler – Best Practices

Do not block callsWaitForSingleObject, CreateFile, RPCs, and othersStrive for lock-free code

Execute work items in a thread poolFollow the MSDN guidelines for specific return codesUse SERVICE_CONTROL_STOP

Call SetServiceStatus(SERVICE_STOP_PENDING)Post stop work to a thread poolCall SetServiceStatus(SERVICE_STOPPED)

SERVICE_REQUIRED_PRIVILEGES_INFO srpInfo;

WCHAR mszPrivilegeBuffer[25] = {0};

hSCManager=OpenSCManager(NULL, NULL, SC_MANAGER_CONNECT);

hFooService=OpenService(hSCManager, wszSERVICENAME, SERVICE_CHANGE_CONFIG);

( VOID ) StringCbCopy ( mszPrivilegeBuffer, sizeof(mszPrivilegeBuffer), L”SeChangeNotifyPrivilege”);

srpInfo.pmszRequiredPrivileges = mszPrivilegeBuffer;

ChangeServiceConfig2 ( *phService, SERVICE_CONFIG_REQUIRED_PRIVILEGES_INFO,

&srpInfo) )

Service Security – Best Practices

Run with the lowest privilege level needed to perform task

Use LocalService/ NetworkServiceAvoid using LocalSystem

Express required privilegesSCM automatically removes all others

Remove unneeded privileges, such as SeImpersonatePrivilege

Task Scheduler(schedule)

Power Efficiency Diagnostics

(powercfg.exe)

Kernel

Detects Idle Condition

Launches Task

Scheduled Task Example

Power Efficiency DiagnosticsPower problem analysisExecutes every 2 weeks when the system is idleRequires SYSTEM privilege to access NT Kernel Logger Saves report data for the userUploads CEIP (Customer Experience Improvement Program) data to Microsoft

Task Triggers

CalendarBootLogonIdleEvent log itemWorkstation lockWorkstation unlock

Task Conditions

Idle conditionStop when not idleAC power onlyStop on batteryWake computer from sleepSpecific or any network connection

Task Recommendations

Use the idle condition to prevent background activity from interrupting the userEnable the power condition – do not run when the system is on batteryEnable the network condition if the task requires network connectivity, such as downloading a software update

Performance and Power

Background activity can degrade PC performanceAdds to the base footprint of the systemInterferes with foreground user activityResource utilization is directly tied to power consumption

Targets when system is idleLess than 2% CPU activityNo disk activity

Evaluate and measure performanceUse XPerfXPerf is part of the Windows Performance Tools Kit

Call to Action

Understand that background activity has tangible impact on system qualitySelect the right model: service or taskUse Windows 7 trigger-start instead of Auto_StartConfigure your service or task to use the most restrictive set of security privilegesLeverage scheduled task idle, power, and network conditionsMeasure using Windows Performance Tools Kit (XPerf)Fill out the evaluation form for this presentation

Resources

Paper - Developing Efficient Background Processes for Windowshttp://go.microsoft.com/fwlink/?LinkId=128622

Paper - Services in Windows Vistahttp://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/Vista_Services.doc

MSDN - Service Control Managerhttp://msdn.microsoft.com/en-us/library/ms685150(VS.85).aspx

MSDN - Task Schedulerhttp://msdn.microsoft.com/en-us/library/aa383614.aspx

Windows Performance Tools Kithttp://www.microsoft.com/whdc/system/sysperf/perftools.mspx

Windows Summit Session - Building High-Performing Windows Applications by Using the Windows Performance Toolkit (SOW-111)

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