Performance Enhancement of Read-only Transactions Using Speculative Locking Protocol T. Ragunathan and Dr. P. K. Reddy
Problems in Processing Read-only Transactions (ROTs) Correctness ( Serializability criteria)
Data Currency ( Transactions receive old values)
Performance ( Throughput)
The performance of 2PL degrades with data contention.
Example:
Snapshot Isolation(SI)-based protocols violate serializability criteria and provide less data currency to ROTs.
Example:
Proposed Speculation based approach (SLR) ROTs are processed with speculation.
Whenever a UT produces after-image, ROTs access both before- and after-images and start speculative executions.
Parameters Values
# of objects in the database 1000
Time to carry out CPU and I/O requests 5ms and 10ms
Size of the largest and smallest ROT 20 and 15 objects
Size of the largest and smallest UT 15 and 5 objects
Simulation Parameters and Values.
Simulation Results
Throughput performance is Improved significantly over SI and 2PL.
0
10
20
30
40
50
60
70
0 20 40 60 80 100
MPL
Th
rou
gh
pu
t
2PL
SIFC
SLR
# UTs 30%- # RUs = 8
Data currency of ROTs improved significantly over SI.
# UTs 30 % , 8 RUs
0
20
40
60
80
100
0 20 40 60 80 100
MPL
Cu
rren
cy
Gain
SLR
SIFC
Requires manageable extra processing resources ( 1.4 times of memory is required).
Conclusions Proposed speculation based approach improves the performance of ROTs significantly over other protocols.
It does not violate serializability criteria.
It processes ROTs without data currency problems.
The experimental results show that it requires manageable ( 1.4t imes) extra processing resources.
Center for Data EngineeringInternational Institute of Information Technology, Hyderabad
http://cde.iiit.ac.in
Example:
Asynchronous Speculative Locking Protocol for improving the performance of Read-only Transactions - T. Ragunathan and Dr. P. K. Reddy
The performance of 2PL degrades with data contention.
Snapshot Isolation(SI)-based protocols violate serializability criteria and provide less data currency to ROTs.
Synchronous speculation based approach (SLR)
Improves performance and data currency. ROTs wait for lock conversion ( EW-lock in to SPW-lock)
Parameters Values
# of objects in the database 1000
Time to carry out CPU and I/O requests 5ms and 10ms
Size of the largest and smallest ROT 20 and 15 objects
Size of the largest and smallest UT 15 and 5 objects
Requires manageable extra processing resources ( 1.5 times of memory is required).
Conclusions
Proposed asynchronous speculation based approach improves the performance of ROTs significantly over other protocols.
It does not violate serializability criteria.
The experimental results show that it requires manageable ( 1.5 times) extra processing resources.
Center for Data EngineeringInternational Institute of Information Technology, Hyderabad
http://cde.iiit.ac.in
Example:
Proposed Asynchronous speculative locking protocol (ASLR) ROTs do not wait for lock conversion and can start executions with the available before-images.
However ROTs perform speculative executions whenever UTs produce after-images. When an ROT commits, it commits with the appropriate speculative execution.
Performance is better than SLR.
Simulation Parameters and Values.
Simulation Results
# RUs = 8, % UTs = 30, MPL = 20
69.008
23.714
6.0581.069
0
20
40
60
80
100
% o
f Tra
nsac
tions 1 Execution
2 Executions4 Executions8 Executions
Throughput performance is Improved significantly over SI, 2PL and SLR.
Example:
0
20
40
60
80
0 20 40 60 80 100
MPL
Th
rou
ghp
ut
2PL
SIFC
ASLR
SLR
# UTs = 30% , # RUs = 8
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