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Constant-Bandwidth Supply for Priority Processing Int. Conf. on Consumer Electronics 2011 Martijn van den Heuvel, Mike Holenderski, Reinder J. Bril and Johan J. Lukkien Systems Architecture and Networking (SAN) Department of Mathematics

SLIDE 1

Constant-Bandwidth Supply for Priority Processing

– Int. Conf. on Consumer Electronics 2011 – Martijn van den Heuvel, Mike Holenderski, Reinder J. Bril and Johan J. Lukkien

Systems Architecture and Networking (SAN) Department of Mathematics and Computer Science Eindhoven University of Technology The Netherlands

11 January 2011

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 1 / 22

SLIDE 2

Outline

1

Media Processing on Virtual Platforms

2

A RELTEQ Approach

3

Constant Bandwidth Supply

4

Conclusions

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 2 / 22

SLIDE 3

Resource constraints and Scalable Media Processing

Today’s CE-devices are heavily loaded: Multiple, independently developed applications

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 3 / 22

SLIDE 4

Resource constraints and Scalable Media Processing

Today’s CE-devices are heavily loaded: Multiple, independently developed applications Trade-off: Quality versus Resources

Reuse software

modules

Cost-effective
Time-to-market

(Porting to new platforms)

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 3 / 22

SLIDE 5

Virtual Platform Objectives

Temporal and spatial isolation, Composition and integration of subsystems on a shared platform. Each subsystem is provided a virtual processor share:

Global Scheduler local scheduler subsystem 0 local scheduler subsystem 1 local scheduler subsystem n

. . .

Subsystem assumptions:

independent subsystems

periodic replenished budget

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 4 / 22

SLIDE 6

Problem Description and Contributions

Hardware virtualization is not for free: 10x increased interrupt latencies and static resource allocation, static resource allocation leads to under-utilization, not (yet) suitable for CE: data-dependent, highly fluctuating load.

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 5 / 22

SLIDE 7

Problem Description and Contributions

Hardware virtualization is not for free: 10x increased interrupt latencies and static resource allocation, static resource allocation leads to under-utilization, not (yet) suitable for CE: data-dependent, highly fluctuating load. We provide software-based support for: light-weight temporal isolation, virtual timers within an application, resource reclaiming.

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 5 / 22

SLIDE 8

Mapping Priority Processing on a Virtual Platform

Global Scheduler local scheduler subsystem 0 local scheduler subsystem 1 local scheduler subsystem n

. . .

B A E time

Quality

Basic 100% B A E time

Quality

Basic 100%

Decision Scheduler

Reclaim unused capacity for enhanced media processing

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 6 / 22

SLIDE 9

Greedy Video Algorithms: Priority Processing

Basic Analyse Enhance time Q u a l i t y Basic Quality (0%) 100%

1. Basic: simple and fast output at

low quality;

2. Analysis: Sort video content

in order of importance;

3. Enhance: Process video content

according to sorted order; Termination is allowed after a basic output is available.

prel. termination

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 7 / 22

SLIDE 10

Priority Processing Example

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 8 / 22

SLIDE 11

Virtual Platforms and Application-level Scheduling

Global Scheduler local scheduler subsystem 0 local scheduler subsystem 1 local scheduler subsystem n

. . .

B A E time

Quality

Basic 100% B A E time

Quality

Basic 100%

Decision Scheduler

Reclaim unused capacity for enhanced media processing

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 9 / 22

SLIDE 12

Mapping Priority Processing on Virtual Platform (Cont.)

20 ms 10 ms 10 ms Legend: server execution task deadline task arrival expiration of a virtual time slot event

Server replenishment period Pb = 10ms Server budget Qb = 5.5ms Video frame rate Pf = 20ms time-slot ∆ts = 1ms (relative to the budget Qb) Assumptions:

Pf is a multiple of Pb

Pf has the same phasing as Pb

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 10 / 22

SLIDE 13

Outline

1

Media Processing on Virtual Platforms

2

A RELTEQ Approach

3

Constant Bandwidth Supply

4

Conclusions

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 11 / 22

SLIDE 14

Relative Timed-Event Queues

We extended a micro-kernel with 2-levels of timer management Basic RELTEQ idea:

2 15 5 4 event queue

Decouple global and local event management:

System Queue: Keep track of global events, e.g. replenishment of server budgets

Server Queue: Keep track of task arrivals

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 12 / 22

SLIDE 15

Extending RELTEQ - Step 1

Decrement heads of all server queues:

56 4 5 3 10 system queue 17 21 server queue 23 5 34 server queue 2 21 4 server queue 3 134 7 1 server queue 12 Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 13 / 22

SLIDE 16

Extending RELTEQ - Step 2

Introduce a Stopwatch Queue: Track the passed time since the last server switch

56 4 5 3 10 system queue 17 21 active server queue 23 5 34 inactive server queues 2 21 4 3 134 7 1 12

Only manage timers for the active subsystem (server).

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 14 / 22

SLIDE 17

Extending RELTEQ - Step 3

On server switch: update all heads of inactive server queues

56 4 5 3 10 system queue 17 21 active server queue 23 5 34 inactive server queues 2 21 4 3 134 7 1 12

stopwatch queue Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 15 / 22

SLIDE 18

Final Setup: Virtual timers

56 4 5 3 10 system queue 17 21 active server queue 23 5 34 inactive server queues & virtual server queus 37 4 3

stopwatch queue 27 5 101 active virtual server queue Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 16 / 22

SLIDE 19

Outline

1

Media Processing on Virtual Platforms

2

A RELTEQ Approach

3

Constant Bandwidth Supply

4

Conclusions

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 17 / 22

SLIDE 20

Constant Bandwidth Servers

Immediately provide new budget when a budget depletes. Postpone deadline (i.e. relative priority of a server).

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 Overhead (% processor time) Number of other applications in the system Virtual Platform Overhead µC/OS-II with CBS µC/OS-II

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 18 / 22

SLIDE 21

Constant Bandwidth Servers and Resource Reclaiming

Immediately provide new budget when a budget depletes. Postpone deadline (i.e. relative priority of a server). First use unused budget of lower priority servers.

Distribution of an SVA’s progress for additional resource availability 0.1 0.2 10 ms 0.1 0.2 Frequency (number of frames) 20 ms 0.1 0.2 10 20 30 40 50 60 70 80 Relative progress (% processed blocks) 30 ms

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 19 / 22

SLIDE 22

Outline

1

Media Processing on Virtual Platforms

2

A RELTEQ Approach

3

Constant Bandwidth Supply

4

Conclusions

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 20 / 22

SLIDE 23

Conclusions

Light-weight virtualization with three-level scheduling Generalized virtual timer concept, providing mechanisms for:

budget enforcement

intra-subsystem budget management

Decoupled global and local event management Minimize overhead of inactive servers’ events Dynamic resource-reclaiming mechanism

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 21 / 22

SLIDE 24

References

L. Abeni and G. Buttazzo.

Integrating multimedia applications in hard real-time systems. In RTSS, Dec. 1998.

C. Hentschel and S. Schiemenz.

Priority-processing for optimized real-time performance with limited processing resources. In ICCE, Jan. 2008.

M. Holenderski, W. Cools, R. J. Bril, and J. J. Lukkien.

Multiplexing real-time timed events. In ETFA, July 2009.

M. M. H. P. van den Heuvel, R. J. Bril, S. Schiemenz, and
C. Hentschel.

Dynamic resource allocation for real-time priority processing applications.

Trans. on Consumer Electronics, 56(2), May 2010.

Martijn van den Heuvel (TU/e, SAN) Constant-Bandwidth Supply for Priority Processing 11 January 2011 22 / 22