CSE 8383 - Advanced Computer Architecture

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CSE 8383 - Advanced Computer Architecture

• Week-13
• April 15, 2004
• engr.smu.edu/rewini/8383

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Contents

• Warm up
• Big Picture
• Clusters
• Scheduling
• Mobile IP
• Reliability issues in Mobile IP

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Group Work
Lets test your network background
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What?
LAN
LAN
Internet
5
Explain
Application
Telnet
ftp
Mail
Presentation
Transmission Control Protocol (TCP)
Session
Transport
Network
Internet Protocol (IP)
Data Link
Token ring
Ethernet
Physical
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Big Picture
7
Leopolds View of the Field
Numerous Application Programs
High
Hiding Details
Low
Concrete Architectures
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Parallel and Distributed Architecture (Leopold,
2001)
SIMD
SMP
CC-NUMA
DMPC
Cluster
Grid
SIMD
MIMD
Shared Memory
Distributed Memory
Degree of Coupling
tight
loose
Supported Grain Sizes
coarse
fine
Communication Speed
slow
fast
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Clusters (Commodity Off The Shelf)
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What is a Cluster?

• A Collection of interconnected stand-alone
  computers working working together as a single
  integrated computing resource
• Cluster nod3es may exist in a single cabinet or
  be physically separated and connected via a LAN

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Clusters
Programming Environment
Middleware
Interconnection Network
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Clusters offer these features

• High Performance
• Expandability and Scalability
• High Throughput
• High Availability

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High Performance Clusters

• Tuned to derive maximum performance
• Share processing load
• Needs software customization
• E.g. Beowulf

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Cluster Components

• Homogeneous Clusters
• All nodes have same configuration
• Heterogeneous Clusters
• Nodes with different configurations e.g.
  different OSs

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Cluster Architecture and OS

• Cluster of PCs
• Cluster of Workstations
• Cluster of SMPs (Symmetric Multiprocessors)
• Linux clusters (Beowulf)
• Solaris clusters (NOW)
• NT clusters

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Cluster Size

• Group clusters 2-99 nodes
• Departmental clusters 99-999 nodes
• Organizational clusters many 100s
• Global clusters 1000s
• Internet wide

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Typical Cluster Environment
User Application
PVM/MPI

• Middleware

OS/Hardware
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PVM MPI

• PVM (Parallel Virtual Machine)
• Allows heterogeneous collection of computers
  linked by a network to be used as a single large
  parallel computer
• MPI (Message Passing Interface)
• Library specification for message passing
• Free and vendor supplied implementations available

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PVM Introduction

• http//www.netlib.org/pvm3/
• http//www.epm.ornl.gov/pvm/
• Started as a research project in 1989
• Developed at Oak Ridge National Lab University
  of Tennessee
• It makes it possible to develop applications on a
  set of heterogeneous computers connected by a
  network that appears logically to user as a
  single parallel computer

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PVM Environment

• Virtual machine
• Dynamic set of heterogeneous computer systems
  connected via a network and managed as a single
  parallel computer
• Computer nodes ? hosts
• Hosts are uniprocessors or multiprocessors
  running PVM software

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PVM Software

• Two Components
• Library of PVM routines
• Daemon
• Should reside on all hosts in the virtual machine
• Before running an application, the user must
  start up PVM and configure a virtual machine

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PVM Application

• A number of sequential programs, each of which
  will correspond to one or more processes in a
  parallel program
• These programs are compiled individually for each
  host in the virtual machine
• Object files are placed in locations accessible
  from other hosts

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PVM Application (Cont.)

• One of these sequential programs, which is called
  the initiation task, has to be started manually
  on one of the hosts
• Tasks on other hosts are started automatically by
  the initiation task
• Tasks comprising a PVM application can be
  identical (SPMD) common in most applications or
  can be different (pipeline input processing,
  output)

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Application Structure

• Start graph
• Middle node is call supervisor or master
• Supervisor-workers or Master-slaves
• Tree
• Root is the top supervisor
• Hierarchy

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Task Creation

• A task in PVM can be started manually or can be
  spawned from another task
• The function pvm_spawn() is used for dynamic task
  creation.
• The task that calls the function pvm_spawn() is
  referred to as the parent
• The newly created tasks are called children.

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To Create a child, you must specify

1. The machine on which the child will be started
2. A path to the executable file on the specified
   machine
3. The number of copies of the child to be created
4. An array of arguments to the child tasks

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Task ID

• All PVM tasks are identified by an integer task
  identifier
• When a task is created it is assigned a unique
  identifier (TID)
• Task identifiers can be used to identify senders
  and receivers during communication. It can also
  be used to assign functions to different tasks
  based on their TIDs

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Task ID Retrieval

• Tasks TID ? pvm_mytid()
• Mytid pvm_mytid
• Childs TID ? pvm_spawn()
• pvm_spawn(,,,,, tid)
• Parents TID ? pvm_parent()
• my_parent_tid pvm_parent()
• Daemons TID ? pvm_tidtohost()
• daemon_tid pvm_tidtohost(id)

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Scheduling
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Scheduling
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Scheduling

• Introduction
• Model
• Program tasks
• Machine
• Schedule
• Execution and communication time
• Problem Complexity

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Introduction to Scheduling

• This problem has been described in a number of
  different ways in different fields
• Classical problem of job sequencing in production
  management has influenced most of the solutions
• Set of resources and set of consumers

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Scheduling System
Consumers
Resources
Scheduler
Policy
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Program Tasks

• (T, lt, D, A)
• T ? set of tasks
• lt ? partial order on T
• D ? Communication Data
• A ? amount of computation

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Task Graph
A
10
5
5
5
8
7
D
E
F
B
C
15
10
20
15
10
5
5
5
4
4
G
H
15
15
20
5
10
I
30
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Machine

• m heterogeneous processors
• Connected via an arbitrary interconnection
  network (network graph)
• Associated with each processor Pi is its speed Si
• Associated with each edge (i,j) is the transfer
  rate Rij

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Examples of Network Graphs
Ring
Linear Array
Fully Connected
Mesh
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Task Schedule

• Gantt Chart
• Mapping (f) of tasks to a processing element and
  a starting time
• Formally
• f T ? 1,2,3, , m x 0,infinity
• f(v) (i,t) ? task v is scheduled to be
  processed by processor i starting at time t

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Gantt Chart
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Execution and Communication Times

• If task ti is executed on pj
• Execution time Ai/Sj
• The communication delay between ti and tj, when
  executed on adjacent processing elements pk and
  pl is
• Dij/Rkl

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Complexity

• Computationally intractable in general
• Small number of polynomial optimal algorithms in
  restricted cases
• A large number of heuristics in more general
  cases
• Quality of the schedule vs. Quality of the
  scheduler

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Mobile Computing
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What is Driving Mobile Computing

• Advances in Wireless Communication Technology
• Advances in Portable Computing Technology
• Reliance on Network Computing
• Mobile Workforce

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Mobile Computing

• Using small size portable computers, hand-helds,
  and other small wearable devices,
• To run applications and access information
  resources via wireless connections
• By mobile and nomadic users

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Mobility versus Nomadicity

• Mobile Node
• The node is able to change its point of
  attachment from one subnet to another while
  maintaining all existing communication.
• Nomadic Node
• The node must terminate all existing
  communication before changing its point of
  attachment.

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Main Components

• Mobile Hosts
• Backbone Network
• Wired
• Wireless Multi-hop
• Hybrid

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Wired Backbone
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Wireless Multi-hop Backbone
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Hybrid backbone
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IETF Mobile IP

• System Components
• Mobile host
• Home address
• Home agent
• Foreign agent (NOT in V6)
• Care of address

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Mobile IP (Cont.)

• Mobile IP Functionality
• Agent Discovery
• Registration
• Tunneling
• Optimization
• Binding Caches
• Foreign Agent Smooth Handoff

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Mobile IP (Cont.)
Foreign Agent
Foreign subnet
Home Agent
Arbitrary Topology of Routers and Links
Home subnet
Mobile Host visiting A foreign subnet
Foreign subnet
Mobile Host at Home
Foreign Agent
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Update in Mobile IP
Mobile Host at Home
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Two-Tier Update

• Can we reduce the cost of update?
• The use of Proxy Agents
• Neighborhood (Location Area)

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Tradeoff Between Update and Search
Mobile Host at Home
Location area