a case for coordinating accuracy-aware applications with power-aware systems
DESCRIPTION
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 PresentationTRANSCRIPT
Department of Computer Science
A Case for Coordinating Accuracy-aware Applications with Power-aware
Systems
Henry [email protected]
Balancing Goals With Programmability
2
Performance Programmability
Balancing Goals With Programmability
3
Performance
ProgrammabilityPower
Lo Hi
Power
Balancing Goals With Programmability
4
Performance
Programmability
Power
Accuracy
Lo Hi
Power
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?
Why Coordinate the Two?
• Avoid bad behavior
• Provide better outcomes than accuracy adaptation alone
• Add new capability to react to environmental changes 6
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
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
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
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)
Avoids Bad Behavior
11
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
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
Support Goals and Goal Changes in Any Two of Three Dimensions
14
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
Questions?
16
Observe Act
Decide
Backup
17
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
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
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
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