Transcript Operating System support for Multimedia

Operating System support for
Multimedia
 QoS (Quality of Service) in Multimedia OS
• Ashish Ranjan
 Multimedia File System
• Jaydeep Punde
 CPU Scheduling in Multimedia OS
• Arun Singal
Operating system
 Operating system is responsible for orderly
and controlled allocation of resources
among the various executing programs
competing for them.
 Main emphasis of commodity OS (unix, NT)
is to reach fairness and efficiency.
 No guarantee given to an application for
timely execution.
Multimedia characteristics
 Multimedia needs real time support.
 If data is not processed at certain pace and
within a certain deadline the data looses
its meaning.
 Adhering to deadlines is desirable but not
absolutely necessary, i.e it is soft real time
in nature.
Problems with existing systems
 Does not support soft real time
characteristic of multimedia stream.
 When real time algorithms applied, other
application starve.
 Need to support all types of application, i.e
both best effort and real time.
Problems Cont.....
 No existing algorithm to satisfy both best
effort and real time need.
 So, how to schedule/reserve resources for
application?
QoS Paradigm
 QoS means to provide reliable and efficient
data delivery service.
 To support all types of application, a
middleware necessary to manage
resources.
 Encompasses both HRT and SRT paradigm.
 Provides probabilistic assurance that
resource requirement will be satisfied a
certain fraction of time.
QoS Requirements
 Multimedia QoS requirement as described
by the high level parameters are
•
•
•
•
Throughput
Delay
Jitter
reliability
Resource Management and QoS
 Tasks
• Specification
– It is concerned with capturing application level
quality of service requirements and management
policies
• QoS mapping
– This is concerned with converting the high level
specification into actual resource level parameters
(low level parameters)
Tasks Contd....
• Admission control
– includes a test whether enough resources are
available to satisfy the request without interfering
with the previously granted request
• allocation 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...
QoS Specification
Application & Protocol threads
Network Connection
Processing
Requirements
Connection requirements
Buffer
Requirements
Operating Systems
CPU
MEM
Network Session manager
NIA
(Network interface adapter)
CONNECTION
Mapping
 Why Mapping is necessary?
 QoS parametres are specified at a high
level
 Exact resource requirement are not known
to application
QoS Mapping
 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 QoS
• 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.
Nemesis
 Designed with a view to support QoS
paradigm
 Single address space to avoid context
swithching
QoS in Nemesis
Application
Adaptation
Instruction
Stream
Desired
performance
QoS
Contoller
QoS
Manager
Application
Execution
Resource
provision
Application
performance
Conclusion
 QoS paradigm encompasses both HRT and
SRT and hence is best suited for
multimedia system.
 QoS should be provided at each layer to
achieve the desired goal.
References:
• [1] Ralf Steinmetz ,"Analyzing the Multimedia Operating
System", IEEE MultiMedia, 2, 1, pp 68-84 (Spring 1995).
• [2] T.Plagemann, V.Goebel, P.Halvorsen, O. Anshus,
"Operating system support for multimedia
systems",Computer communications,23,3,pp 267289,(2000).
• [4] P. Goyal and X. Guo and H. Vin "A hierarchical CPU
scheduler for multimedia operating systems ", In
Proceedings of the Second Symposium on Operating
Systems Design and Implementation (OSDI). USENIX,
October 1996.
References:
• [5] Schulzrinne, H., "Operating System Issues for
Continuous Media," Multimedia Systems, vol. 4, pp.
269--280, Oct. 1996.