1. Process/Code Migration and Cloning
CS 314 Operating Systems
Process/Code Migration and Cloning
Department of Computer Science
Southern Illinois University Edwardsville
Fall, 2018
Dr. Hiroshi Fujinoki
Migration/001

2. CS 314 Operating Systems Migration & Cloning Migration
Only one active copy can exist at a time
Process/Code Segment
Transferred
Migration/002

3. CS 314 Operating Systems Migration & Cloning Cloning
Multiple active copies can exist at a time
Process/Code Segment 
Transferred  
The same portions of a process can be executed in parallel
Migration/003

4. CS 314 Operating Systems Why Code/Process Migration and Cloning
To distribute processor usage
(jobs at a processor (or a “computer host”) can be moved to another processor)
To reduce data transmission delay
(Example: networked graphic-based applications)
Data
Process
Migration/004

5. CS 314 Operating Systems Why Code/Process Migration or Cloning
To distribute processor usage
(jobs at a processor (or a “computer host”) can be moved to another processor)
To reduce data transmission delay
(Example: networked graphic-based applications)
Process
Process
Data
Migration/005

6. Metrics for Code/Process Migration and Cloning
CS 314 Operating Systems
Decision-making Factors
 When to transfer code?
 Which code to transfer?
 Where to transfer code?
“Transfer Policy” deal with this
“Selection Policy” deals with this
“Location Policy” deals with this
Metrics for Code/Process Migration and Cloning
Short-Term
Scheduler Queue
Processor
Processor
Processor
Process/Code
(a) Processor
Utilization
(b) Degree of
Multitasking
(c) Scheduler
Queue Length
Migration/006

7. CS 314 Operating Systems Code and Process Migration Remote Host
Local Host
Remote Host
Process
Migration
Transmission
(Migration)
Delay ()
Local Execution Time ()
Remote
Process ()
Transferring
results
Transmission
(Migration)
Delay ()
Migrated Execution Time
=  +  +
Migration/007

8. Each process consists of:
CS 314 Operating Systems
Code and Process Migration
What can be migrated ()?
What can not be migrated ()?
Each process consists of: 
 Program codes
(machine instruction codes) 
 Program data and data structures
(heap and stack memory areas) 
 Local resources reserved and being used
by this process
 - Depends on types of process/code migration
Migration/008

9. Total Time using Process Migration ()
CS 314 Operating Systems
Code and Process Migration
Process
Code Migration:
Only a portion of a process is migrated
Code
Migration
Local Host
Remote Host
Code
Code
Migration
Total Time using Process Migration ()
Remote
Process ()
Transferring
results
Local Execution Time ()
Transferring
results
Advantages
(1) Migration delay can be improved
(2) Less processor resource needed in a remote host
(3) Execution time using migration () takes less time
Migration/009

10. CS 314 Operating Systems Models for Process/Code Migration Weak
Internal Execution
(as Target Process)
Models for Process/Code Migration
Sender-Initiated
(PUSH Model)
External Execute
(as Separate Process)
Weak
Mobility
Strong
Receiver-Initiated
(PULL Model)
Internal Execute
(as Target Process)
External Execution
(as Separate Process)
Code
Migration
Migrate Process
Sender-Initiated
(PUSH Model)
Clone Process
Migrate Process
Clone Process
Receiver-Initiated
(PULL Model)
Migration/010

11. CS 314 Operating Systems Weak Mobility
Process/code migration where only the program codes are transferred
Code Migration:
Process Migration:
Segments of code must be started from its initial state
(from the state it has not been started)
Whole processes must be started from its initial state
(e.g., only a function in a program is remotely executed)
Process/Code Segment
Transferred
Any pre-generated parameter value can not
be migrated (must start with initialization)
It’s not necessary where to start
Any migrated code or process must start with
its initial state
Migration/011

12. CS 314 Operating Systems Strong Mobility
Process/code migration where both program codes and data structures
are transferred
Process/Code Migration:
A migrated segment of code can be:
Started at any point
Stopped at any point
Resumed at any point
Process/Code Segment
Migrated
Migrated
Migration/012

13. CS 314 Operating Systems Summary: Code/Process Mobility Weak Mobility
Strong Mobility
 Only program codes
 Program codes
What are migrated?
 Data to be processed
When to migrate?
 Before execution only
 Any time
(after a program starts
running, it can be
migrated any time)
Migration/012

14. CS 314 Operating Systems Internal & External Execution
Migrated code/process
are executed w/in the
remote-host software’s
address space
Internal Execution
Example: Java-Script
Remote Host
Software
Local Host
Remote Host
Process/Code Segment
Transferred
Migration/013

15. CS 314 Operating Systems Internal & External Execution
The new process/code
is executed as a new
independent process
Example: various “plug-ins”
(e.g., Adobe Flash Player)
External Execution
Remote Host
Software
Request
Transferred
(the name of the program)
Data to be processed transferred
Process/Code Segment
Local Host
Remote Host
 A local (origin) host requests a program to
start at a remote host.
 A local (origin) host sends data to be processed
at a remote host after the program starts
at a remote host.
New process
is created
Migration/014

16. CS 314 Operating Systems Push and Pull Models Push Model
When the current processor’s utilization or waiting queue length exceeds
some threshold, the current busy processor requests another processor to
adopt some code or processes
Push
Pull
When a processor’s utilization or waiting queue length goes below
some threshold, the idle processor requests other processors to migrate
some code or processes
Migration/015