Os Vandeven

Programming for Low Power: It's everyone's responsibility Arjan van de Ven Software and Solutions Group July 25th, 2007

The next 45 minutes ,[object Object],[object Object],[object Object]

Why software matters for power ,[object Object],[object Object],[object Object],[object Object]

What consumes power in a PC ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Race-to-idle Save power by running at the highest speed ,[object Object],[object Object],[object Object],Half speed Full speed

Race-to-idle Save power by running at the highest speed ,[object Object],[object Object],[object Object],[object Object],Lesson: Do things as fast as you can so that the system can be idle longer

Sleep duty cycle ,[object Object],[object Object],[object Object],= !=

Sleep duty cycle ,[object Object],!= Lesson: Stay in idle for long periods of time Avoid interrupting idle as much as possible

Software spoils the game ,[object Object],[object Object],[object Object],[object Object],Current software is misbehaving and wasting power

Enemy #1: Polling ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Frequent polling causes spattergroit

Enemy #2: Timers ,[object Object],[object Object],[object Object]

Enemy #2: Timers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Group timer events system wide but not internet wide

Enemy #3: Disk IO ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Java / C# / Python / Ruby / ... ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Special case: Media playback ,[object Object],[object Object],[object Object],[object Object],[object Object],Use large buffers for multimedia

Tools: PowerTOP and strace ,[object Object],[object Object],[object Object]

C/P/T states ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

C states ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],185us 1.2 W C4/C5 85us 7.7 W C3 10us 12.9 W C2 0 13.5 W C1 34 W / 25 W C0 Latency Power C state

P states ,[object Object],[object Object],[object Object],[object Object],[object Object]

T states ,[object Object],[object Object],[object Object],[object Object]

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