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Department of Computer Science A Case for Coordinating Accuracy- aware Applications with Power-aware Systems Henry Hoffmann [email protected]

A Case for Coordinating Accuracy-aware Applications with Power-aware Systems

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A Case for Coordinating Accuracy-aware Applications with Power-aware Systems. Henry Hoffmann [email protected]. Balancing Goals With Programmability. Performance. Programmability. Lo. Hi. Power. Balancing Goals With Programmability. Power. Programmability. Performance. Lo. - PowerPoint PPT Presentation

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Page 1: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Department of Computer Science

A Case for Coordinating Accuracy-aware Applications with Power-aware

Systems

Henry [email protected]

Page 2: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Balancing Goals With Programmability

2

Performance Programmability

Page 3: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Balancing Goals With Programmability

3

Performance

ProgrammabilityPower

Lo Hi

Power

Page 4: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Balancing Goals With Programmability

4

Performance

Programmability

Power

Accuracy

Lo Hi

Power

Page 5: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Partial Solutions

5

Per

form

ance

Per

form

ance

Accuracy Power

Accuracy-aware Applications(e.g. DynamicKnobs, Quality-of-Service Profiling, EnerJ, Petabricks, Eon, Green)

Power-aware Systems(e.g. Maybe too many to list PTRADE, METE, ControlWare,

Agilos, Swift)

Each is provably optimal individually. What happens when they interact?What guarantees can we provide?

Page 6: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Why Coordinate the Two?

• Avoid bad behavior

• Provide better outcomes than accuracy adaptation alone

• Add new capability to react to environmental changes 6

Page 7: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Why Does Bad Behavior Arise?

7

Pow

er (

W)

Acc

urac

y Lo

ss (

%)

Configuration

x264 Video Encoder

PowerAccuracy Loss

Accuracy-aware application prefers perfect accuracy, at high power

Power-aware system prefers saving power, at high accuracy loss

Page 8: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Example Of Bad Behavior

• Run x264 (video encoder) on real Linux x86 system with

• Problem is performance becomes a non-linear (and non-convex) function of application and system

8

Page 9: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Why Run Both?

9

Combining accuracy- and power-awareness leads to:

1) Better energy efficiency for same accuracy or

2) Better accuracy for same energy efficiency

Page 10: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

How Can We Solve This Problem? [ECRTS 2014]

• Split into multiple dimensions: lead and subordinate• Control lead• Dynamically construct controller for subordinate• Subordinate controller approximates linearity

10

PowerController

PowerTranslator

Application &System

-

PerformanceController

PerformanceTranslator-

gp(t)

gs(t)

ep(t)

es(t)

up(t)

us((t)ks(t)

kp(t)

fs(t)

fp(t)

Page 11: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Avoids Bad Behavior

11

Page 12: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Reacts to Application Resource Needs

• Video with three distinct scenes• Coordination reacts to phases while:

– Maintaining real-time performance– Reducing power consumption– Providing higher accuracy

12

Page 13: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Reacting to Changing Goals

13

0 50 100 150 200 2500

0.5

1

1.5

2

Norm

alize

d

Perf

orm

an

ce

0 50 100 150 200 2500

1

2

3

4

Norm

alize

d

Pow

er

0 50 100 150 200 2500

1

2

3

4

Accu

racy

Loss

Real-time, Low-power Real-time, High Accuracy

Page 14: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Support Goals and Goal Changes in Any Two of Three Dimensions

14

Page 15: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Conclusions

• Coordination of adaptive applications and systems is necessary

• Possible with cascading control systems

• Cascading control:– Avoids bad behavior– Provides better outcomes– Provides greater responsiveness to

fluctuations in workload and changes in goals

15

Observe Act

Decide

Page 16: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Questions?

16

Observe Act

Decide

Page 17: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Backup

17

Page 18: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Selecting the lead dimension

• The lead dimension becomes the one with fewer “knobs” (options)

• The subordinate dimension has more options

• Intuition:– After controlling lead, there will still be knobs affecting

subordinate 18

Page 19: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Controlling the Lead Dimension

• 5-7 compute a control action• 8-19 ensure that:

– Goal met in lead dimension – Affects on subordinate dimension are optimal

• Intuition:– Anything we do in the lead should have smallest affect on subordinate

19

Page 20: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Constructing a Subordinate Controller

• Approximate affect of lead dimension on subordinate (20)

• Construct controller based on this approximation (21)

• Intuition:– Approximate non-linear interaction by constructing tangent to

true curve– Converges to true behavior (analogous to derivative in

calculus)

20

Page 21: A Case for  Coordinating  Accuracy-aware Applications with Power-aware Systems

Controlling the Subordinate Dimension

• 22-33 ensure control for subordinate does not affect lead

• Also, control should be optimal in any remaining dimensions

• Intuition:– Use subordinate actions that do not affect lead 21