Optimizing Power and Energy

Lei Fan, Martyn Romanko

Motivation

31% of TCO attributed to power and cooling Intermittent power constraints

Renewable energy Grid balancing

20% - 30% utilization on average Green: good for the environment Green: saves money

Themes

Hybrid (hardware/software) optimizations Dynamic DRAM refresh rates (Flikker) Dynamic voltage/frequency scaling (MemScale) Distributed UPS management Power cycling (Blink)

Software optimizations Dynamic adaptation (PowerDial)

Flikker: Saving DRAM Refresh-power through Critical Data Partitioning Partitioning of data into critical vs. non-critical Partitioning of DRAM into normal vs. low refresh

rates Programming language construct

Allows marking of critical/non-critical sections Primarily software with suggested hardware

optimizations OS and run-time support Refresh rate optimizations

Flikker

MemScale: Active Low-Power Modes for Main Memory Modern DRAM devices allow for static scaling MemScale adds:

DVFS for MC; DFS for memory channels and DRAM devices Policy based on power consumption and

performance slack

MemScale

Managing Distributed UPS Energy for Effective Power Capping in Data Centers Use of distributed UPSs to sustain peak power loads Based on existing distributed UPS models

Larger batteries needed for longer peak spikes Allows for more servers to be provisioned

Analysis of effect on battery lifetime Argued benefit outweighed cost of extra batteries Lacked detailed analysis on cooling costs

Blink: Managing Server Clusters on Intermittent Power Reducing energy footprint of data centers Power-driven vs. workload driven

Blink: power-driven technique Metered transitions between

High power active states Low power inactive states

Blink

Three policies Synchronous: optimizes for fairness Activation: optimizes for hit rate Load-proportional: both

Unknown effects of power cycling on component lifetime

PowerDial: Dynamic Knobs for Power-Aware Computing When is this applicable for a program?

QoS (accuracy) vs. power/performance tradeoff Subject to system fluctuations

Dynamic tuning of program parameters Adaptable to fluctuations in power/load

Determines control variables Application Heartbeats framework provides

feedback Automatic insertion of API calls

PowerDial

Discussion, Questions?