philips research 1st meeting of project ees.5653 15 june 2015 alina albu, [email protected] tu/e...

April 18, 2023 Alina Albu, [email protected]

TU/e Computer Science, System Architecture and NetworkingPhilips Research Laboratories Eindhoven

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1st meeting of project EES.5653

Quality of Service for In-Home Digital Networks

PROGRESS PROJECT EES.5653

Terminal QoS

M.A. Weffers-Albu



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Contents

• Project goals

• Approach

• Description of analyzed systems

• Trimedia Streaming Software Architecture

• A characterization of streaming applications execution

• DVD player case study

• Future work



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QoS in IN-Home Digital Networks

Network

Aim: provide guaranteed and optimised Quality of Service (QoS) for interconnected real-time embedded systems.

Prediction

&

Optimisation

of

Performance Attributes:

AT, RT, NCS, RU.

Terminal QoS:

Reliability

&

Performance

Predictability of system.



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Component-based Real-Time Embedded Systems

…

… …

…

…

Physical Platform

Goals•Nearly optimised design for optimal resource utilization of the subsystems involved (good performance).

•Interference limited - reduced to a minimum through good design practices (good reliability).

•Fast integration of pre-designed subsystems.



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…

… …

…

…

Physical Platform

Challenges

Scarcity of resources

Resource sharing

Low Predictability

Non-guaranteed Reliability & Performance



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…

… …

…

…

Physical Platform

Approach

Resource requirements

Resource reservations

Virtual Platforms

Guaranteed resource availability

while

Resource usage restricted to a

configured maximum.

VP1 VP2

VPn-1 VPn



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Approach

1. Derive the VPs of the subsystems involved by predicting performance quality parameters (NCS, AT, RT, RU) for each of the subsystems. (Specifications in terms of behaviour and performance).

2. Control performance quality parameters - find good practices of design for the subsystems so that their resources needs can be satisfied on the physical platform.

Example:

• Predict the number of context switches (NCS) – the overhead occurring during the execution of a system.

• Give guidelines for priority assignment such that the NCS is minimized.



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Approach

3. Resources needs - strongly related to events that occur during the execution of a subsystem.

Repetitive patterns of events => Execution predictable

Identify the patterns of events during the execution of a subsystem…

· the conditions under which the events adopt repetitive patterns…

· the relations between the patterns of events.



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…

EQ EQ

FQ

EQ

FQC1

C2 Cn

FQ…

Empty Queue

Full Queue Full Queue

Empty Queue

Component

Processing code

Get Full Packet Put Full Packet

Put Empty Packet Get Empty Packet

Typical execution scenario of a TSSA component

- get 1 FP from input FQ,

- get 1 EP from input EQ,

- processing,

- put 1EP in output EQ.

- put 1FP in output FQ.

TriMedia Streaming Software Architecture



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TriMedia Streaming Software Architecture TSSA components

Data driven. Execution determined by:

- Availability of necessary input

- Priority of component task

- Data driven with blocking due to communication with hardware. Execution determined by:

- Availability of necessary input

- Average blocking time

- Time driven. Execution determined by:

- Availability of necessary input. (Or NOT)

- Priority

- Periodicity.



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TriMedia Streaming Software Architecture TSSA components

All types. Execution determined by:

- Average computation time.

- n->m relation between input and output.

- If m variable – average m or distribution over time for the values of m.

- Average times needed to get each input FP/EP.

- Average times needed to produce each output FP/EP.



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A characterization of streaming applications execution.

Theorem

Let C1, C2, C3, …, Cn be a chain of components communicating through a set of queues as in Figure 1. Provided that the components are designed such that their execution in the chain does not lead to deadlock, and provided that the input is sufficiently long, the execution of the components in the chain will adopt a repetitive pattern after a finite number of steps.

Hyperperiod

Initialization

Phase

Stable

Phase

Finalization

Phase



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Definitions• Initialization phase – the interval of time until the execution of the components

reaches a repetitive pattern.

• Stable phase - the interval of time during which the all components execute according to a repetitive pattern.

• Hyperperiod – the interval of time needed for the execution of the repetitive pattern.

• Finalization phase – interval of time following the stable phase. The finalization phase starts when the first component does not have input anymore and finishes its execution. During the finalization phase the last transactions in the queues are completed and all the components are stopped



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Chain:

- N data driven components

- n->m: 1->1

- priorities in descending order.

EQ EQ

FQ

EQ

FQ

C1C2 CN

FQ

P(C1) > P(C2) > …> P(CN)

…

C1C2 CN…

Initialization phase:C1: executes until output FQ is filled=> C1 - Blocked (b).

C2(p)C1(b), C2(p)C1(b), …, until C2(b) (FQ filled, EQ empty)C1(b),

C3(p)C2(p)C1(b) C2(b), C3(p) C2(p)C1(b) C2(b)… C3(p) C2(p)C1(b) C2(b), C3(b)

CN(p)CN-1(p)… C2(p)C1(b)C2(b)…CN-1(b),

Hyperperiod

Stable phase:CN(p)CN-1(p)… C2(p)C1(b)C2(b)…CN-1(b),



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DVD player case study

FRead VDec SSE VO

EQEQ

FQ

EQ

FQFRead VDec SSE VO

FQ

P(FRead) > P(VDec) > P(SSE) > P(VO)

FRead

- Data driven with blocking

VO

-Time driven

- 1->2

VDec

-Data driven

-1->m, m variable

SSE

-Data driven

-1->1



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DVD player case study

NCS_hyperperiod(FRead) = 5,

NCS_hyperperiod(VDec) = 9,

NCS_hyperperiod(SSE) = 8,

NCS_hyperperiod(VO) = 8.

the total NCS_hyperperiod = 5+9+8+8 =30;

In order to validate our results we measure the NCS on a duration of the stable phase equal with 30 hyperperiods.

NCS_StablePhaseMeasured = 895;

NCS_StablePhaseCalculated = 900;



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Current & Future Work

Current Work• Proof “Stable State Theorem” in a general case of components

types combinations.• Provide design guidelines for optimizing the NCS, RU• Find patterns in the input stream that can be related to the

pattern of execution.

Future Work • Analyze patterns of memory access, bus utilization• Find relations between memory accesses, bus utilization and

the pattern of execution.• Provide ways for controlling the above patterns.• Consider multi-processor platforms.

philips research 1st meeting of project ees.5653 15 june 2015 alina albu, [email protected] tu/e...

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