Transcript Implementation and Evaluation of a Multimedia File System

Implementation and Evaluation of a
Multimedia File System
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T.N.Niranjan
Tzi-cker Chiueh
Gerhard A. Schloss
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Department of Computer Science
State University of New York at Stony Brook
1997 IEEE
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Presented by Sharon Shen
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OVERVIEW
Introduction
 Related Work
 MMFS Design
 Performance Evaluation
 Conclusions and future work
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INTRODUCTION
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Multimedia unique demands in file system
MMFS extends UFS
Supports a two dimensional file structure
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Single medium editing
Multiple-media playback environments
A fully functional file system based on the
VFS
INTRODUCTION
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Classification of multimedia applications
– Playback oriented
 Concerned with real-time constraints
and synchronized retrieval
– Development oriented
 Require system support to manipulate
compositions
INTRODUCTION
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MMFS offers a set of functionalities
for multimedia support
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Synchronized multi-stream retrieval
Editing support
Caching and prefetching optimizations
Real-time disk scheduling
RELATED WORK
UCSD multimedia server
 CMFS
 Mitra & SBVS
 IBM Tiger Shark
 YARTOS
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RELATED WORK
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Tactus toolkit & Acme I/O Server
Audition audio system
MMFS could not provide real-time
guarantees to multimedia playback
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Vagaries of the FreeBSD process scheduler
Lack of admission control
Re-implementation on Unix OS augmented with
real-time support make this feature feasible
MMFS DESIGN
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Extends the UNIX file structure
– A single-medium strand abstraction
– An MM file construct: tie multiple strands
– An MM file is associated with unique
mnode
 Mnode
contains the metadata of the MM file
 Mutimedia-specific metadata of each strand
(recording rate,logical block size, the size of
the application data unit)
MMFS DESIGN
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Reduction of the “impedance
mismatch” between the multimedia
applications and the file system
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Used for low-level optimization
MMFS API
 Add
an extra argument mminfo
 Add/Remove strands from an MM file
 Insert/Delete data from strands
MMFS DESIGN
Prefetching
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Unix file system
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Sequential reads are common
Each open file is associated with a readahead length(v_ralen) in its vnode
Not sequential readprefetching is avoid
and exponential back-off of v_ralen is
initiated
MMFS DESIGN
Prefetching
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Playback of a video in reverse
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UFS identify non-sequential
readreduce the degree of prefetching
MMFS allows the application to advise
the file system reverse the direction
 Setting
mminfo->direction to REVERSE
 Passing mminfo as an argument to mmread
MMFS DESIGN
Prefetching
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Playback of a video in fast-forward
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UFS Prefetching ( issue read-aheads for
unnecessary blocks)
MMFS DESIGN
Prefetching
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Playback of a video in fast-forward
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MMFS perform intelligent prefetching
 Applications
communicate MMFS
 Setting the fields in mminfo (retrieval
rate,direction,whether frames skip)
 Degree of prefetching is maintained at a high
level
Note: It does not work for compressed data
streams
MMFS DESIGN
Prioritized real-time disk scheduling
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UFS using SCAN
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Order the request by the position of the
requested physical block on the disk
surface
nonRT operations queued with RT
multimedia operations
MMFS DESIGN
Prioritized real-time disk scheduling
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MMFS using priority
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Higher priority = RT request, lower priority =
nonRT request
Non-preemptive Scheduling
Assign a deadline with each mmread request
Use Earliest Deadline First scheduling for RT
use SCAN for nonRT request
Starvation possible for nonRT
MMFS DESIGN
Support for synchronization
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Quality of synchronization measured by the
amount of skew
MMFS considers each strand as a
temporally continuous stream of data
Specify mmbind, synchronized retrieval the
given strands
MMFS constructs a round-robin retrieval
schedule for these strands
An mmunbind call issued when
synchronization is no longer required
MMFS DESIGN
Support for Editing
UFS use write, truncate system calls
for small size file
 Multimedia editing large
uncompressed files
 MMFS provide mminsert and
mmdelete
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MMFS PERFORMANCE EVALUATION
Evaluation Environment
Multimedia data residing in local IDE
disk of Pentium-90
 Compare MMFS with UFS of FreeBSD
2.0.5
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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization
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Parameters of experiment
MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization
Response Time: time taken between
the issuance of read request and the
reception of the request data
 Delayed: If the response time is more
than 130% of the frame duration
 Performance metric: fraction of
delayed frames
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MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization
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Reverse playback
MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization
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Fast forward playback
MMFS PERFORMANCE EVALUATION
Impact of prefetching optimization
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Fast reverse playback
MMFS PERFORMANCE EVALUATION
Impact of prioritized RT disk scheduling
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Effect of nonRT load
MMFS PERFORMANCE EVALUATION
Impact of prioritized RT disk scheduling
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Effect of RT load
MMFS PERFORMANCE EVALUATION
Impact of synchronization support
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Multi-Strand Playback
MMFS PERFORMANCE EVALUATION
Impact of synchronization support
CONCLUSIONS & FUTURE WORK
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UFS assumptions and design decision are
not appropriate for multimedia
MMFS prefetching optimization allow
applications to playback streams at higher
access rate and different directions
MMFS disk scheduler maintains the
performance of the multimedia application
when RT and nonRT application are
simultaneously active
CONCLUSIONS & FUTURE WORK
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MMFS editing primitives offer an excellent
response to development applications
MMFS bridges the gap between generic file
systems and special-purpose servers
MMFS provides real-time process
scheduling to meet QoS requirements
CONCLUSIONS & FUTURE WORK
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The idea embedded in MMFS are widely
applicable to any general-purpose file
system
Many enhancements to the current
implementation are possible
The impact of variable-rate compression on
MMFS optimizations have to be studied
The feasibility of extending MMFS to a
distributed environment deserves
investigation
REFERENCES
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Niranjan, T. N. File System Support for multimedia
applications. PhD thesis, SUNY at Stony Brook,
December 1996. At
http://www.cs.sunysb.edu/~niranjan/thesis.ps.gz
Niranjan, T. N. and Schloss. F. State-based buffercache design for a multimedia file system. In Proc.
Of the Sixth Int. Workshop in Network and
Operating System Support for Digital Audio and
Video(NOSSDAV), April 1996
Q&A
Thank You !