ICCPS 2012 1 Dionisio de Niz, 1 Lutz Wrage, 2 Nathaniel Storer, 2 - - PowerPoint PPT Presentation
On Resource Overbooking in an Unmanned Aerial Vehicle ICCPS 2012 1 Dionisio de Niz, 1 Lutz Wrage, 2 Nathaniel Storer, 2 Anthony Rowe, and 2 Raj Rajkumar 1 Software Engineering Institute 2 Electrical & Computer Engineering Carnegie Mellon
On Resource Overbooking in an Unmanned Aerial Vehicle
1Dionisio de Niz, 1Lutz Wrage, 2Nathaniel Storer, 2Anthony Rowe, and 2Raj Rajkumar 1Software Engineering Institute 2Electrical & Computer Engineering
Carnegie Mellon University
ICCPS 2012
2
Surveillance Coverage Collision Avoidance Takeoff-to-Surveillance Distance Route Planning Flight Control Amount of Intelligence
Safety-Critical Mission-Critical
(Prevent Damage) (Provide Value)
true
3
Mission-Critical Reserve
Safety-Critical
Mission-Critical
Conservative approach over-allocates resources to safety-critical tasks
Safety-Critical Reserve (Based on Worst-Case)
4
Underutilized Most of the Time
Mission-Critical Reserve
Safety-Critical
Mission-Critical
Safety-Critical Reserve
Conservative approach underutilizes resources
5
Used for mission-critical most of the time
Mission-Critical Reserve
Safety-Critical
Mission-Critical
Reclaim unused resources & use them to optimize utility of mission-critical tasks while preserving timing guarantees of safety-critical tasks
Safety-Critical Reserve
Overbooking
6
t1 t2
2
½
2.5 2 4 8 Task Period Criticality WCET NCET t1 Surveillance Cov. 4 Mission 2 2 t2 Collision Avoid. 8 Safety 5 2.5
2
7
t1 t2
2
½
2.5 2 1 1 4 8 Task Period Criticality WCET NCET t1 Surveillance Cov. 4 Mission 2 2 t2 Collision Avoid. 8 Safety 5 2.5
Zero-Slack Instant
8
t1 t2
2
½
2.5 2 1 1 4 8 Task Period Criticality WCET NCET t1 Surveillance Cov. 4 Mission 2 2 t2 Collision Avoid. 8 Safety 5 2.5
Overbooking
9
t1 t2
2
½
2.5 Task Period Criticality WCET NCET Utility t1 Surveillance Cov. 4 Mission 2 2 {2,2.5} t2 Collision Avoid. 8 Safety 5 2.5 t3 Amount of Intelligence 4 Mission 2 2 {2,2.5}
t3
4 8
Reclaimed Resources
10
t1 t2
2
½
2.5 1 1 Task Period Criticality WCET NCET Utility Levels t1 Surveillance Cov. 4 Mission 2 2 {2,2.5} t2 Collision Avoid. 8 Safety 5 2.5 t3 Amount of Intelligence 4 Mission 2 2 {2,2.5}
t3
1 1
1 2 2 2.5 2 2.5 1 2 Resource Utility Utility
4 8 1 1 Total Utility = 2.5
Utility Diminishes: Utility ≠ Criticality
11
t1 t2
2
½
2.5 1 1 Task Period Criticality WCET NCET Utility Levels t1 Surveillance Cov. 4 Mission 2 2 {2,2.5} t2 Collision Avoid. 8 Safety 5 2.5 t3 Amount of Intelligence 4 Mission 2 2 {2,2.5}
t3
1 1
1 2 2 2.5 2 2.5 1 2 Resource Utility Utility
Total Utility = 4
ZS-QRAM: More mission-critical utility from same resources
4 8
12
2 4 6 8 10 100%
13
2 4 6 8 10 100%
14
Period degradation Suspend lower utility
15
Period degradation Suspend lower utility
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Overload Vector Deadline Misses utility
Overload Vector Deadline Misses Utility Meet deadline Meet deadline?
Scheduler favors high utility Scheduler does not favor high utility
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18
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Low-Level Flight Control Actuation Task Sensor Data Task Aux Sensor Data Video Navigation Task Object Detection Task Video Streaming Task httpd crond ntpd
Safety Critical Mission Critical Non-Real-Time
21
Task Util1 Util2 C Co T1 T2 ZS Actuation 1 1 30 30 Sensor Data 0.1 0.1 65 65 Aux Sensor Data 0.5 0.5 50 50 Navigation 11 11 50 49 Object Detection 7 15 40 100 87 Video Streaming 2 4 10 10 120 40 40
All figures in milliseconds
22
Nominal Overloaded
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24
25
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CPS requires new scheduling mechanisms that can cope with uncertainty in the environment (variable execution time) Criticality-based overbooking protects safety-critical tasks allowing them to steal cycles from mission-critical ones
ZS-QRAM optimizes mission-critical value
Developed a metric that captures the capacity of the scheduler to retain utility in overloads Demonstrated in a surveillance mission on our drone-rk platform