Socket Swapping for efficient distributed communication between migrating processes

MS Final DefensePraveen Ramanan

12th Dec 2002

Introduction

What is Process Migration?The mechanism of transferring a process

between two machines during its execution

What is Socket Migration? The mechanism of transferring one end of

a live connection from one host to another without loss or interruption to the packet flow

Need for Socket Migration

Lack of Network Socket Migration at the Operating System Level

MOSIX, its importance with socket migration

MOSIX and its characteristics

Software that can transform a Linux cluster of x86 based workstations and servers to run almost like an SMP

Has the ability to distribute and redistribute the processes among the nodes

Process Migration in MOSIX

User-level

Kernel

Link Layer

User-level

Kernel

Link Layer

Deputy

Remote

Local

process

A local process and a migrated process

Solution: Kernel Socket Swapping

Processes in machine A and B Communicate

through Sockets

Process migrates to Machine C

Process then communicates

through C library

SocketSwap is calledAfter communication

Communication is re-established

between the processes

A

B

C

Technologies/Tools Used

User Mode Linux (UML) Aglets JNI (Java Native Interface)

Sockets

OS interface that allow communication between two different processes on same or different machines

Behaves much like a low-level file descriptor

Identified by a host.port pair

System calls

Entry points through which an active process obtain services from the kernel

Distinction between user mode and kernel mode

Context switch done by generating a software interrupt

Socket related System Calls

Socket() Bind() Listen() Connect() Accept() Read() and Write() Close()

Socket Strucuture

struct socket{

socket_state state;unsigned long flags;struct proto_ops *ops;struct inode *inode;struct fasync_list

*fasync_list;struct file *file;struct sock *sk;wait_queue_head_t wait;short type;unsigned char passcred;

}

Writing the System Call

Implemented in User Mode Linux, a safe secure way of running linux versions and linux processes

Why UML?

UML is a virtual machine which runs linux inside linux

Debugging and testing becomes easy Protects the main linux machine from

abnormal crashes

Features of UML

It has a fully functional kernel It has hardware support It has access to host file system It is completely configurable, allowing

its memory, available devices to be specified

Mobile agents and aglets

Have unique ability to transport themselves from one system to another

Aglets are java objects that can move from one host to the other

Aglets takes the program code as well as data during its movement

Testing the System Call through aglets and JNI

Aglets are made to communicate through a C library (C library uses sockets) through JNI

During communication, aglets are made to move from one machine to another

System call is called and the socket is swapped

The communication of the moved aglet is then established with the swapped socket

4.Local C library communicates with C library of the remote machine.

4

2.Aglet B moves from one machine to another. 2

3.AgletB Contacts the HaveMoved() of the local C library

3

1. Aglets A and B are communicating within the same machine thru Send and Recv Fns of C library API 1

5.system call swaps the socket

5

6.New Communication is established between the processes after socket swap.

6

Results (Data Size:400MB)

Latency(sec)

BandWidth(Mbps)

Mosix 67.918 47.1204

Normal Linux

TCP UserModeLinux

35.658

51.946

89.74

61.60

SocketSwap 52.786 60.62

Questions?

Acknowledgements

Dr Daniel Andresen Dr Gurdip Singh Dr Mitchell Neilsen