Energy-Efficient Software Criteria

Published:04/05/2012   Last Updated:04/05/2012

Energy-Efficient Software Criteria

Download Software Criteria (PDF)

Checklist for creating software applications that is energy-efficient. The checklist is operating system-agnostic except where otherwise noted.


Computational Efficiency

Loops

  • Minimized the use of tight loops?
  • Converted polling loops to being event driven?
  • Using efficient polling loops (largest possible polling interval) when polling loops are necessary?
  • Eliminated busy wait (spinning) loops, where possible? Might still be required for certain locking/synchronization tasks.

Performance Libraries/Extensions

  • Utilizing instruction set extensions (such asSSE instructions, AVX, or newer) to accelerate computations?
  • Utilizing Performance Libraries such as Intel® Performance Primitives or Intel® Math Kernel Library?
  • Utilizing on-chip video encode/decode hardware acceleration using Intel® HD Graphics and the Intel® Media Software Development Kit (Intel® Media SDK)?


Algorithms

  • Using high performance algorithms and data structures (gets the job done faster)?
  • If requirements allow, can you select a less complex algorithm that is more power efficient?
  • Minimized use of heavily recursive algorithms (these can be power inefficient)?


Compiler Optimization Options

  • Is application optimized for speed?
  • Is application optimized (profiled) for most common execution path?


Drivers

  • Utilizing kernel/drivers that are idle power friendly?
  • Identified drivers causing excessive interrupts?


Programming Language

  • Using a programming language implementation and libraries that are idle power friendly?


Maximize Idle

Multithreading

  • Taking advantage of multiple threads and cores to speed-up execution? Faster execution means more time to idle.
  • Are threads balanced? Imbalanced threads may increase power consumption.


Reduce usage of High-Resolution Periodic Timers

  • Using a timer rate appropriate for the application? Intervals < 15ms have low benefit on most systems and serve only to reduce idle times. Always make sure to disable periodic timer in case it is not in use.
  • If application increases the timer tick rate when active, remember to reset to default timer value when idle? For Microsoft* Windows*, the default system timer resolution is 15.6ms.
  • (Linux) Using timer APIs in application so that timers can be grouped (e.g. round_jiffies) or utilizing deferrable kernel timers?


Data Efficiency

  • Can data be pre-fetched from optical disk and buffered, allowing disk to idle?
  • Can data be pre-fetched from hard-disk and buffered, allowing disk to idle?
  • Avoiding frequent reads/writes to disk?
  • Can read/write requests be batched into one operation?
  • Using algorithms that minimize data movement, memory (cache versus RAM), and hierarchies that keep data close to the processor?
  • Identified processor resources shared between cores? Synchronize threads on different cores to work simultaneously and idle simultaneously.


Context-Aware (Power-Aware) Behavior

Handling Sleep Transitions Seamlessly

  • Is application preventing/delaying system sleep or hibernate state transitions? Make sure to handle appropriate transition events.
  • (Microsoft* Windows*) Are you preventing System Idle Timeouts only when necessary? Remember to reset execution state when task is complete (SetThreadExecutionState).


Respond/Adapt to System Power Events

  • Responding to transition between battery and AC operation?
  • Handling Low Battery event by saving work/state/checkpoint? Avoid duplicating work in case of standby.
  • (Windows) Responding to PBT_APMSUSPEND within two seconds?
  • Application adapting to user selected OS power policy?


Scale Behavior Based on Machine Power State

  • Can resource usage be reduced when on battery power (such as avoiding background updates)?
  • Is it possible switch to “low-power” algorithms on Low Battery?
  • Depending on machine state, have you explored the option of letting the application inform the user to select a low(er) power profile for efficient execution?
  • Utilizing context awareness toolkits such as Intel® Mobile Platform SDK, Intel® Laptop Gaming TDK, or Intel® Web 2.0 TDK?
  • Can unused peripherals be shut off/disabled (e.g. Bluetooth*, 802.11) if no activity?


Testing for Energy-Efficiency

Profile system power during application runtime

  • Understand the power impact of application at Idle and Running state
  • Examine C-state behavior
  • Examine P-state behavior
  • Examine timer interrupts
  • Examine interrupt statistics
  • Examine disk and file access statistics


 

Tools
Intel® Power Checker (platform timer tick, idle power efficiency, power-awareness  
Perfmon Microsoft * Windows* XP, Windows Vista*, Windows 7
PwrTest/Windows Driver Kit Microsoft Windows XP, Windows Vista, Windows 7
Windows Event Viewer (Timer tick change events,
Microsoft-Windows-Kernel-Power\Diagnostic log)
Microsoft Windows XP, Windows Vista, Windows 7
Intel® PowerInformer Microsoft Windows XP, Windows Vista, Windows 7
Windows ETW (performance monitoring framework) Microsoft Windows XP, Windows Vista, Windows 7
Intel® Application Energy Toolkit Microsoft Windows XP, Windows Vista, Windows 7, Linux, Apple* Mac OS*
PowerTOP Linux
Battery Life Toolkit (BLTK) Linux
Linux command-line tools: strace, blktrace, iostat, etc. Linux


For details on the above topics and references to existing white papers and articles, please refer to the extended document, Energy-Efficient Software Guidelines. This checklist created by Intel as a general suggestion. If you have feedback, suggestions, or would like more information about power management go to http://www.intel.com/software/power/.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

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