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SRDS’03
Performance and Effectiveness Analysis of
Checkpointing in Mobile Environments
Xinyu Chen and Michael R. Lyu
The Chinese Univ. of Hong Kong
Hong Kong
Florence, Italy
CUHKSRDS’03
Outline
Introduction A mobile environment – Wireless CORBA Performance analysis with and without
checkpointing Analytical results and comparisons Conclusions
CUHKSRDS’03
Introduction
Checkpointing and Rollback Recovery Checkpointing
Save program’s states during failure-free execution
Repair bring the failed device back to normal operation
Rollback reload the program’s states saved at the most recent
checkpoint
Recovery Reprocess the program, starting from the most recent
checkpoint by applying the logged messages, until the point just before the failure
CUHKSRDS’03
Wireless CORBA Architecture
Visited Domain
Home Domain
Terminal Domain
Access Bridge
Access Bridge
Access Bridge
Access Bridge
Static Host
Static Host
Terminal Bridge
GIOP
Tunnel
ab1
ab2
mh1
GTP Messages
Control messageComputational message
GIOP: General Inter-ORB Protocol
GTP: GIOP Tunnel Protocol
CUHKSRDS’03
Wireless CORBA Architecture
Visited Domain
ab1
ab2
Access Bridge
Access Bridge
Static Host
Static Host
Home Domain
Home Location
Agent
Terminal Domain Terminal
Bridge
GIOP
Tunnelmh1
mh1
Terminal Domain Terminal
Bridge
GIOP
Tunnel
GIOP
Tunnel
mh1
Terminal Domain Terminal
BridgeGIOP Tunnel
mh1
Terminal Domain Terminal
Bridge
Access Bridge
Access Bridge
Handoff: a mechanism for a mobile host to seamlessly
change a connection from one Access Bridge to another
CUHKSRDS’03
Program’s Termination Condition
GTP messages Control message Computational message: the number is not changed
A program on a mobile host is successfully terminated if it continuously receives n computational messages
Formulate the expected program execution time with message number n
CUHKSRDS’03
State Transition without Checkpointing
State 0 – normal, State 1– repair, State 2 – handoff
0
2 1
Generally distributed random variables H: handoff time R: repair time
CUHKSRDS’03
Expected Program Execution Time
Expected repair time
Expected program execution time without checkpointing
Laplace transform for cumulative distribution function
CUHKSRDS’03
Equi-number Checkpointing
Take checkpoints according to the number of received messages (a)
Divide the program execution into m equal intervals (m=n/a) Equi-number checkpointing with respect to message
number Message number in each checkpointing interval is not changed
Equi-number checkpointing with respect to checkpoint number
Checkpoint number is not changed
CUHKSRDS’03
State Transition in Equi-number Checkpointing
State 3 – Composite repair State 4 – Composite checkpointing
0
2
3
4/a
A generally distributed random variable C: Checkpointing time
CUHKSRDS’03
Composite States
State 3 – Composite repair State 5 – repair, State 6 – rollback, State 7 – handoff
5 6 7
3
State 4 – Composite checkpointing State 8 – checkpointing, State 9 – handoff
4 8 9
6 7
9
CUHKSRDS’03
Expected Program Execution Time
Expected sojourn time in State 3
Expected program execution time with equi-number checkpointing
= m
CUHKSRDS’03
Average Effectiveness
Effective interval: a program produces useful work towards its completion
Wasted interval: Repair and rollback Handoff Checkpoint creation Wasted computation
Average Effectiveness: how much of the time an MH is in effective interval during an execution
CUHKSRDS’03
Optimal Checkpointing Interval
Minimize the expected program execution time or maximize the average effectiveness
CUHKSRDS’03
Analytical Results and Comparisons (1)
Equi-number checkpointing with respect to checkpoint number
CUHKSRDS’03
Average effectiveness vs. message arrival rate and handoff rate
Analytical Results and Comparisons (3)