Operating System support Operating System support for Multimediafor Multimedia

QoS (Quality of Service) in QoS (Quality of Service) in Multimedia OSMultimedia OS• Ashish RanjanAshish Ranjan

Multimedia File SystemMultimedia File System• Jaydeep PundeJaydeep Punde

CPU Scheduling in Multimedia OSCPU Scheduling in Multimedia OS• Arun SingalArun Singal

Operating system Operating system

Operating system is responsible for Operating system is responsible for orderly and controlled allocation of orderly and controlled allocation of resources among the various executing resources among the various executing programs competing for them.programs competing for them.

Main emphasis of commodity OS (unix, Main emphasis of commodity OS (unix, NT) is to reach fairness and efficiency.NT) is to reach fairness and efficiency.

No guarantee given to an application No guarantee given to an application for timely execution.for timely execution.

Multimedia characteristicsMultimedia characteristics

Multimedia needs real time Multimedia needs real time support.support.

If data is not processed at certain If data is not processed at certain pace and within a certain deadline pace and within a certain deadline the data looses its meaning.the data looses its meaning.

Adhering to deadlines is desirable Adhering to deadlines is desirable but not absolutely necessary, i.e it but not absolutely necessary, i.e it is soft real time in nature.is soft real time in nature.

Problems with existing Problems with existing systemssystems

Does not support soft real time Does not support soft real time characteristic of multimedia characteristic of multimedia stream.stream.

When real time algorithms applied, When real time algorithms applied, other application starve.other application starve.

Need to support all types of Need to support all types of application, i.e both best effort and application, i.e both best effort and real time.real time.

Problems Cont.....Problems Cont.....

No existing algorithm to satisfy No existing algorithm to satisfy both best effort and real time both best effort and real time need. need.

So, how to schedule/reserve So, how to schedule/reserve resources for application?resources for application?

QoS ParadigmQoS Paradigm

QoS means to provide reliable and QoS means to provide reliable and efficient data delivery service.efficient data delivery service.

To support all types of application, a To support all types of application, a middleware necessary to manage middleware necessary to manage resources.resources.

Encompasses both HRT and SRT paradigm.Encompasses both HRT and SRT paradigm. Provides probabilistic assurance that Provides probabilistic assurance that

resource requirement will be satisfied a resource requirement will be satisfied a certain fraction of time.certain fraction of time.

QoS RequirementsQoS Requirements

Multimedia QoS requirement as Multimedia QoS requirement as described by the high level described by the high level parameters areparameters are• ThroughputThroughput• DelayDelay• JitterJitter• reliabilityreliability

Resource Management Resource Management and QoSand QoS

TasksTasks• SpecificationSpecification

– It is concerned with capturing application level quality of service requirements and management policies

• QoS mappingQoS mapping– This is concerned with converting the high

level specification into actual resource level parameters (low level parameters)

Tasks Contd....Tasks Contd....

• Admission controlAdmission control– includes a test whether enough resources are

available to satisfy the request without interfering with the previously granted request

• allocation and schedulingallocation and scheduling– This is where actual resources are allocated and

scheduled

• Accounting/Policing– implies tracking down the resources consumed

by the task

• Deallocation

Task Contd...Task Contd...

Operating Systems Network Session manager

CPU MEM NIA CONNECTION (Network interface adapter)

Application & Protocol threadsProcessing BufferRequirements Requirements

Network Connection

Connection requirements

QoS Specification

MappingMapping

Why Mapping is necessary?Why Mapping is necessary? QoS parametres are specified at a QoS parametres are specified at a

high levelhigh level Exact resource requirement are Exact resource requirement are

not known to applicationnot known to application

QoS MappingQoS Mapping

Scaling Scaling • As the data passes trough different

layers of protocol, protocol headers are attached to the frame, which increases its size, and hence scaling of required application bandwidth is done

Delay Partioning• The delay is partitioned across each

module.

Bottlenecks for providing Bottlenecks for providing QoSQoS

• QoS should be supported at all layers of communication

• Data packets from the network are processed in First in first out basis for all connection

• Kernel do a lot of hidden processing with high priority

• The layered architecture of the communication systems may imply considerable data movement in the protocols

• Accounting in OS.

NemesisNemesis

Designed with a view to support QoS paradigm

Single address space to avoid context swithching

QoS in NemesisQoS in Nemesis

QoS Contoller

ApplicationAdaptation

ApplicationExecution

QoS Manager

Desiredperformance

Resourceprovision

InstructionStream

Applicationperformance

ConclusionConclusion

QoS paradigm encompasses both QoS paradigm encompasses both HRT and SRT and hence is best HRT and SRT and hence is best suited for multimedia system.suited for multimedia system.

QoS should be provided at each QoS should be provided at each layer to achieve the desired goal.layer to achieve the desired goal.

References:References:

• [1] Ralf Steinmetz ,"Analyzing the Multimedia [1] Ralf Steinmetz ,"Analyzing the Multimedia Operating System", IEEE MultiMedia, 2, 1, pp 68-Operating System", IEEE MultiMedia, 2, 1, pp 68-84 (Spring 1995).84 (Spring 1995).

• [2] T.Plagemann, V.Goebel, P.Halvorsen, O. [2] T.Plagemann, V.Goebel, P.Halvorsen, O. Anshus, "Operating system support for Anshus, "Operating system support for multimedia systems",Computer multimedia systems",Computer communications,23,3,pp 267-289,(2000).communications,23,3,pp 267-289,(2000).

• [4] P. Goyal and X. Guo and H. Vin "A hierarchical [4] P. Goyal and X. Guo and H. Vin "A hierarchical CPU scheduler for multimedia operating systems CPU scheduler for multimedia operating systems ", In Proceedings of the Second Symposium on ", In Proceedings of the Second Symposium on Operating Systems Design and Implementation Operating Systems Design and Implementation (OSDI). USENIX, October 1996.(OSDI). USENIX, October 1996.

References:References:

• [5] Schulzrinne, H., "Operating System [5] Schulzrinne, H., "Operating System Issues for Continuous Media," Multimedia Issues for Continuous Media," Multimedia Systems, vol. 4, pp. 269--280, Oct. 1996.Systems, vol. 4, pp. 269--280, Oct. 1996.