PowerSpy: Fine Grained Power Profiler

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PowerSpyFine Grained Power Profiler

• Kutty S Banerjee
• Emmanuel Agu

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Mobile Devices Energy Crisis

• Rate of Growth of
• CPU
• Memory
• Disk Space
• Wireless Transfer Speed
• Far Greater than that of Battery Energy !!

Powerful Change Part1Batteries and Possible
Alternatives for the Mobile Market. IEEE
Pervasive Computing,October-December 2003 (Vol.
2, No. 4)
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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?
• ltApplication initiated I/Ogt

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PowerSpy Features

• Non Intrusive of Kernel Source
• Non Intrusive of Application Source
• Software-Only
• Accurate Billing sans OS activities
• Windows 2000,XP,Server 2003

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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

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Thread and I/O Profiling
Thread Power Usage
Device Power Usage
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Procedural Profiling
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Application Profiled

• OpenVRML
• VRML Browser (disk heavy)
• Graphics appln.
• Mozilla
• I/O heavy (Network heavy)
• Windows Media Player
• I/O heavy (Network heavy)

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Background Work
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Power Measurement Approaches

• Measure Power Loss - Application Runtime
• Hardware (PowerScope)
• Software (PowerSpy)
• Break Application Runtime -gtFinite Elements
• Power Consumption Finitie Elements Known prior
• Sum to get total power

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PowerScope Approach

• Hardware multimeter measures current, voltage.
• Samples PC, PID, ISR
• Analysis offline

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OS Context Switches

• Time of execution of threadquantum
• Need to monitor current thread of execution as
  often as quantum period
• What about preemption? Well see next

System Architecture
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Scheduler vs KTracker
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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()

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I/O Devices (Overlap with CPU)
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I/O Device Monitor
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I/O Device Monitor

• Question -gtDo you check all I/O Devices live in
  system ?
• Push on stack question until Implementation!!
• Question -gt What if thread does overlapped I/O
  with n devices?
• Limitation of PowerSpy. We cannot distinguish b/w
  them!!

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Overlapped I/O
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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!!

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Implementation Overview
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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 10msroughly equal to
  Windows standard quantum.
• Every 10ms, DPC preempts Scheduler and executes
  algorithm.
• 10ms NOT GUARANTEED EXACT!!Windows is NOT REAL
  TIME!!

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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) -gt
  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

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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!!

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Reference

• Inside Windows 2000
• Programming Applications for MS Windows
• Windows Loader Matt Pietrik
• www.sysinternals.com
• www.osronline.com
• Powerscope
• Windows DDK

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Questions