Ho-Ramammorthy 2 phase
snapshot algorithm
PRESENTATION
Chao Ma
Kent State University
November 25th 2013
Outline
Introduction
 Algorithm Summary
 Experimental Setup





Main program
Test program
Conclusions
Result


Graphics
Output Results
Future work
 Code defense

Introduction



The point of this experiment is to test the efficiency
of Ho and Romamoorthy Two-Phase deadlock
detection algorithm by using two methods below:
vary the number of sites of basic algorithm message
exchanges to test the frequency of deadlocks
vary the number of sites of basic algorithm message
exchanges to test consuming time
Algorithm

every site maintains a status table, containing status of all local
processes
 resources held, resources waiting on

periodically, coordinator requests all status tables, builds a
WFG, and searches it for cycles
 no cycles - no deadlock
 If cycle is found, coordinator again requests all status
tables, again builds a WFG, but this time uses only those
edges common to both sets of status tables
Experimental Setup

Main program

The main program have two parts, one is message passing system
that is a process of sending and receiving messages, another is
deadlock detector system that updates message passing system and
detect the cycle by only using id common to both sets, this process
is like a WFG graph.
Message
passing
system
Deadlock
detector
system
Output of
deadlock
detect
Experimental Setup

Test program

The role is to test the frequency and time consumming of deadlock
detection algorithm by varying numbers of sites.
Deadlocks compute function
Deadlock
detector
system
Varying numbers of sites
Time record function
The result
output of all
tests
Experimental Setup

Conclusions

Through analysing and comparing by varying numbers of sites, the
result could be reflected as two changing curves.
With the increase of numbers, the curve of frequency of deadlock
detection is steady increase, however every time of test result
reflects floating different that need many times of test to make an
accurate statistical result
With the increase of numbers, the time consuming curve is slightly
increase and to some extent depend on the effect of processing speed
of PC


Show result

Graph
The numbers of sites (id)
Show result

Graph
The number of sites(id)
Show result
Future work



To simulate my program on a real distributed network
to search for deadlocks
To test my program with much larger number of
processes that could make the statistics more precise
To observe its performance based on various and
complex message passing situation
Reference

"Advanced Concepts in Operating Systems" by Mukesh
Singhal and Niranjan G. Shivaratri

K.M. Chandy, J. Misra, and L.M. Haas "Distributed deadlock
detection", ACM Transactions on Computer Systems, 1(2), pp
141-156, May 1983
Questions?
Thank you