Jiwon Hahn
ECE295 Seminar
December 2, 2002
Integrated Management of Power Aware Computing & Communication Technologies
IMPACCT Project People
Faculty: Pai Chou, Nader Bagherzadeh
Students: Jinfeng Liu, Dexin Li, Bita Gorji-Ara, Duan Tran,
and Jiwon Hahn
Collaborator NASA JPL, Rockwell Collins, ISI
Sponsors DARPA PAC/C, Broadcom, HP
Outline What is IMPACCT? Motivation How it works Tools Experiments and Results Conclusions and Future Works
What is IMPACCT? A CAD tool for exploring
power/performance tradeoffs A new technique that performs component,
system, and mission-level integrated power management
Target applications Mars pathfinder, ATR, UCAV,…
Motivation Embedded Systems
Computers inside devices PDA, cellphone, camera, vehicles, robots,…
Power management Power-Aware vs. Low-power Mission-Aware: meet the constraints
High-level approach Amdahl’s law: Power saving of a component must be
scaled by its percentage contribution to entire system Evaluate combined effects in the context of system Higher abstraction level enables global optimum
How it works Hierarchical power management System-level power scheduling
Power-aware scheduling Mode selection
Mission-level power scheduling Schedule Selection
Scheduling & Mode Selection Power Aware Scheduling
Schedules tasks, meeting timing and power constraints Output: initial schedule Static scheduling/planning [DAC'01]
Mode Selection Selects resource modes of each task considering mode
dependency Minimize energy consumption Output: mode schedule
Mode selection/modeling [ASPDAC’02] Winner Best Student Paper Award
Schedule Selection Goal
To generate a mission level schedule which Adapts to variable power constraint Considers higher-level context change overhead Meets the global deadline
Assumptions A mission contains one or more applications It is static
Schedule Selection Problem:
Select N schedules among M different
schedules, by deadline D, under the maximum
power curve P.
Minimize energy considering overhead
0 1 2 … M
…
Schedule Set
D
P
Put N schedules here!
0 1 … M
0
1
…
M
Overhead MatrixCurrent schedule
Previous Schedule
Schedule Selection(cont.) Parameters: t,n,k,m
t: timestamp. (discrete value) 0tD
n: schedule count excluding S0 1nN
k: schedule count including S0.
(for tracking the selected path) 1kD m:current schedule 0mM
Schedule Selection(cont.) Algorithm: 4D Dynamic Programming
n
k
m
t = D
t =2
t =1
n
m
t
Idea: Reach the global optimum by keeping track of optimal solutions of subproblems
Optimal substructure For some(k,m), min{E(t,n,m)} contains the optimal value.
Space D3 for keeping optimal Energy
D4 for bookkeeping indices
Speed O(D3) – polynomial!
Could be optimized for speed-up
Energy CubeBookkeeping
Cubes
Schedule Selection(cont.) Notation
Set of schedule, S= {S0, S1, … ,SM}
Time period of each schedule: Ts[0…M] Power level of each schedule: Ps[0…M] Energy of each schedule: Ts x Ps = Es[0…M] Schedule-switch overheads from Si to Sj:
Po(i,j), To(i,j), Eo(i,j)
Schedule Selection(cont.) Algorithm
Initialization If (t,n,k,m) is the first possible selection,
E(t,n,k,m) = directly calculated energy Else
E(t,n,k,m) = Process
if m!=0, E(t,n,k,m)=E(t’,n-1,k-1,m’)+Eo(m’,m)+Ps(m)Ts(m) t = t’+To(m’,m)+Ts(m)
if m=0, E(t,n,k,m)= E(t’,n,k-1,m’)+Eo(m’,m)+Ps(m)Ts(m)
System-level Input:
Application Model ports, channels,…
Architecture Model System architecture template Component library + mode dependency model(MDM)
Constraints Power and Timing
Output: Mode Schedule
Mission-Level
Mission-level Constraints: Power and Deadline
Mission Schedule
System-level1
App. Model Constraints
Sys. Arch. Template
Component Library+ MDM
Mode Schedule
1)
Schedule Selector
Mission-Level2
Mission Constraints
Overhead Calculator
Mission Schedule
MS MS MS MS MS …Schedule Collector
2
Scheduler
Initial Schedule
Mode Selector
1
System-level
• Initial Schedule:
• Mode Schedule:
Mission-Level
Mission Power Constraint Curve
Mission Deadline
• Mission Schedule:
Tools Scheduler (Jinfeng) Mode Selector (Dexin) Schedule Selector (Jiwon) Etc.. Programs and tutorial are available
Tools(I): Scheduler
Tools(II): Mode Selector
Tools(III): Schedule Selector
Mars Rover Comparison over 3 scenarios
Overall mission 3 power scenarios: best, typical, worst, 10 min each 48 steps
Power-aware schedules Accelerated speed by tracking available power Finished earlier before working in the worst case 33% faster, 32.7% less energy cost
Experiments and Results I
Experiments and Results I(cont.)
Experiments and Results II Mars Rover
Behaviors and tasks Moving around on Mars surface Communicating with the Lander Taking pictures Performing scientific experiments
Components in the entire system Hazard detector, Driving motor, Steer motor,
Radio frequency modem (RF), Camera (CAM), Microprocessor (PPC), Micro-controller
Experiments and Results II(cont.) On/off only
Relaxed constraints Mode change overhead No max power constraint
Mode selection Energy saving:
From 6.9% to 49.3% average 26.5%
Meets max power
0
100
200
300
400
500
600
700
800
900
1000
5 6 7 8 9 10
Mode Selection
On&Off
Pmin (W)
Energy (J)
Experiments and Results III Example of Schedule Selection
0 1 2 3
0
1s 1s 3s 4s
0J 4J 7J 6J
0W 4W 21W 24W
1 ?
1s
? ?4J
4W
2 ?
2s
? ?5J
10W
3 ?
3s
? ?10J
30W
20s
3
0-3 13-1
10s, 5J, 50W 5s, 10J,
50W
3s, 15J, 45W
0 1 2 3
• Schedule Set:
• Overhead Matrix
Experiments and Results III(cont.)
30-3 13-1
20-2 12-1
1 120s
20s
20s
Low Power
Greedy
Dynamic Programming
Exceed deadline
Energy = 149W Nonoptimal solution
Energy = 131W Optimal solution!
Experiments and Results III(cont.)
Run-time Deadline Guarantee
Energy optimization
Manual N/A X X
Low Power constant X X
Greedy linear X X
Enumeration exponential O O
Dynamic Programming
polynomial O O
Conclusions IMPACCT
greatly expands the range of power/performance trade-offs
effectively integrates existing power management techniques
models system-level dependencies saves great amount of energy consumption while
meeting all constraints proposes novel hierarchical power management
technique
Current & Future Works Ongoing work
Architecture Modeling(Dexin) Mission-level Power Management(Jiwon) Extended experiments on broadcom and itsy
board(Jinfeng) Applying to different application: SDR(Bita)
Future work Dynamic Power Management Mixed application schedule selection More applications
Reference Pai H. Chou, Jinfeng Liu, Dexin Li, and Nader Bagherzadeh, “IMPACCT: Methodology and Tools for Power-
Aware Embedded Systems”, Design Automation for Embedded Systems J. Liu, P. Chou, N. Bagherzadeh, and F. Kurdahi. “Power-aware scheduling under timing constraints for
mission-critical embedded systems”. In Proc. 38th Design Automation Conference, pages 840–845, June 2001 D. Li, P. Chou, and N. Bagherzadeh. Mode selection and mode-dependency modeling for power-aware
embedded systems. In Proc. 7th Asia South Pacific Design Automation Conference, pages 697–704, January 2002
J. Hahn, P. Chou, and N. Bagherzadeh, “Tutorial: IMPACCT Tool v1.0”, University of California at Irvine, August, 2002
THANK YOU!
THANK YOU!