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PowerSpy: Fine Grained Power Profiler. Kutty S Banerjee Emmanuel Agu. Mobile Devices – Energy Crisis. Rate of Growth of CPU Memory Disk Space Wireless Transfer Speed Far Greater than that of Battery Energy !!.

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Powerspy fine grained power profiler

PowerSpy:Fine Grained Power Profiler

Kutty S Banerjee

Emmanuel Agu


Mobile devices energy crisis

Mobile Devices – Energy Crisis

  • Rate of Growth of

    • CPU

    • Memory

    • Disk Space

    • Wireless Transfer Speed

      Far Greater than that of Battery Energy !!

Powerful Change Part1:Batteries and Possible Alternatives for the Mobile Market. IEEE Pervasive Computing,October-December 2003 (Vol. 2, No. 4)


Powerspy

PowerSpy

Helps answer the following questions:

  • Which Thread consumes How much power?

  • What procedures in each thread are invoked?

  • Which I/O Device consumes how much power?

    • <Application initiated I/O>


Powerspy features

PowerSpy Features:

  • Non Intrusive of Kernel Source

  • Non Intrusive of Application Source

  • `Software-Only’

  • Accurate Billing sans OS activities

  • Windows 2000,XP,Server 2003


Powerspy usage

PowerSpy Usage

  • Installation:

    • Powerspy.sys (kernel mode driver)

      • Installation Requires Administrative Privilege

    • Powerspy.exe (user mode application)

    • Windows XP (run checked build)

      • Boot option `/debug’ flag set

  • Usage:

    • powerspy devenv.exe (Microsoft Visual Studio)

    • Produces `report.dat’ . Results next…


Thread and i o profiling

Thread and I/O Profiling

Thread Power Usage

Device Power Usage


Procedural profiling

Procedural Profiling


Application profiled

Application Profiled

  • OpenVRML

    • VRML Browser (disk heavy)

    • Graphics appln.

  • Mozilla

    • I/O heavy (Network heavy)

  • Windows Media Player

    • I/O heavy (Network heavy)


Background work

Background Work


Power measurement approaches

Power Measurement Approaches

  • Measure Power Loss - Application Runtime

    • Hardware (PowerScope)

    • Software (PowerSpy)

  • Break Application Runtime ->Finite Elements

    • Power Consumption Finitie Elements Known prior

    • Sum to get total power


Powerscope approach

PowerScope Approach

  • Hardware multimeter measures current, voltage.

  • Samples PC, PID, ISR

  • Analysis offline


Os context switches

OS Context Switches

  • Time of execution of thread=quantum

  • Need to monitor `current thread of execution’ as often as quantum period

  • What about preemption? We’ll see next…

System Architecture


Scheduler vs ktracker

Scheduler vs KTracker


Pseudo code algorithm

Pseudo Code Algorithm

if(measurePowerOn_==true)

{

if(currentThread_!=SchedulerThread())

measurePowerOn_=false;

tempPower_=instPower_;

instPower_=measurePower();

totalPower_=tempPower_-instPower_;

}

else

{

if(currentThread_==SchedulerThread())

{

measurePowerOn_=true;

instPower_=measurePower();

}

}


I o devices overlap with cpu

I/O Devices (Overlap with CPU)


I o device monitor

I/O Device Monitor


I o device monitor1

I/O Device Monitor

  • Question ->Do you check all I/O Devices live in system ?

    • Push on stack question until Implementation!!

  • Question -> What if thread does overlapped I/O with `n’ devices?

    • Limitation of PowerSpy. We cannot distinguish b/w them!!


Overlapped i o

Overlapped I/O


What about procedures

What about Procedures?

  • Two Approaches?

    • Invasive – Add stub of code in executable in each procedure for all modules

      • Stub merely records itself!!

    • NonInvasive – Simply check PC at sampled intervals. (POWERSPY APPROACH)

      • Use Module Export/Import Table

      • Base Loading Address

        For address to module,procedure translation!!


Implementation overview

Implementation Overview


Windows scheduling policy

Windows Scheduling Policy

  • Preemptive Priority driven.

  • Get current thread running (last running) PsGetCurrentThreadId (kernel mode call)

  • To monitor Scheduler

    • Need to be at same priority

    • Must be non preemptable by Scheduler

    • DPC (Deferred Procedure Calls) execute at same priority as Windows Scheduler called `Dispatcher’

    • Timed DPC running at 10ms=roughly equal to Windows standard quantum.

    • Every 10ms, DPC preempts Scheduler and executes algorithm.

    • 10ms NOT GUARANTEED EXACT!!Windows is NOT REAL TIME!!


Monitor i o operations

Monitor I/O Operations

  • All user mode appln do I/O by Win32 API

  • Win32 API forwards request to I/O Manager

  • I/O Manager creates IRP (I/O Request Packet) and forwards to appropriate Device Driver.

  • For every thread( user mode or kernel mode), internal OS data structure (undocumented) -> ETHREAD.

  • ETHREAD contains list of IRPs thread currently blocked on.

  • IRP contains name of I/O Devices.

  • Therefore, thread to I/O Device located!!

  • ETHREAD maintained in `ntoskrnl.exe’. Not Exported!! Therefore need `debug symbols’. Hence need to run `checked build of Windows’.

  • Have access to Internet!! Symbol Server of Microsoft at http://msdl.microsoft.com


Limitations

Limitations

  • Thread Blocked on I/O Device DOES NOT mean I/O Device currently executing its order!!

  • I/O Device has internal queue.

  • Thread 4 blocked and billed but not actually serviced!! Excess Power billed!!

  • Procedures NOT CALL GRAPH!!


Reference

Reference

  • Inside Windows 2000

  • Programming Applications for MS Windows

  • Windows Loader – Matt Pietrik

  • www.sysinternals.com

  • www.osronline.com

  • Powerscope

  • Windows DDK


Questions

Questions


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