Process Migration Group A4 Min Fang Bryan Maden Chris Sun 1 Outline Definition Motivation Mechanisms Security Sand box model 2 What is process Migration Transfer of sufficient amount of the state of a process from one machine to another The process executes on the target machine 3 Motivation Load sharing Move processes from heavily loaded system to lightly loaded system Communication performance Processes that interact intensively can be moved to the same node to reduce communication cost 4 Motivation Availability long running process may need to move because the machine it is running on will be down 5 Process Migration Mechanisms Who initiates the migration What happens to outstanding messages and signals What portion of the process is migrated 6 Example What is migrated 7 Example What is migrated 8 What is migrated Eager all Transfer entire address space No trace of process is left behind It could be unnecessarily expensive if address space is large and the process does not need most of it 9 What is migrated Precopy Process continues to execute on the source code while the address space is copied Pages modified on the source node have to be copied a second time reduce the process frozen time 10 What is migrated Eager dirty Transfer only portion of the address space that is in main memory and have been modified Any additional blocks of the virtual address space are transferred on demand The source machine is involved throughout the life of the process 11 What is migrated Copy on reference Pages are only brought over on reference Variation of eager dirty Has lowest initial cost of process migration 12 What is migrated Flushing Pages are cleared from main memory by flushing dirty pages to disk Relieves the source of holding any pages of the migrated process in main memory 13 Secure Process Migration Protect the migrating process Impossible to fully protect all kinds of attacks Possible to detect modifications Ajanta system Read only state Append only logs Selective revealing Protect the target Sand box model Playground model 14 Sandbox model Provide a restricted environment to confine the behavior of a process instead of eliminating process execution failures Each instruction of the migrated process can be fully controlled 15 JAVA Security Mechanism The Class Loader download into correct name space tagged with security info The byte code verifier check if the untrusted code obey the security rules of the sandbox The security manager authenticate the mobile code and makes the decision 16 Reference Tanenbaum and Steen Distributed Systems Principles and Paradigms Stallings Operating Systems 4th edition 17
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