Use Case Scenarios for Performance Control of Grid-based Metacomputing

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Use Case Scenarios for Performance Control of
Grid-based Metacomputing

• John Gurd, Ken Mayes, Graham Riley
• 3rd Grid Performance Workshop, June 2005

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Overview

• Preamble
• The case for Performance Control
• Context
• Malleable, component-based Grid applications
• The PERCO (Performance Control) System
• Design and implementation
• Homogeneous Components
• Simple performance control scenarios
• More Complex Scenarios
• Conclusions

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Achieving Performance

• Engineering for maximum performance
• coarse design, then fine tuning
• requires high degree of repeatability
• benefits from homogeneity, symmetry, etc.
• Control to achieve (less than maximum) target
• use negative feedback control at run-time
• necessary to approach dynamic environment
• helps to deal with heterogeneity

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How to Control Performance?

• Requires (negative) feedback
• needs sensors, actuators and compensators
• timers, control handles, predictive models
• Whole system vs. piece-wise control
• who is responsible for what?
• Perception is that a hierarchy is needed
• hence need hierarchical software structure

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Controllable Components?

• Several groups have suggested that control should
  be effected via a component-based software
  architecture
• degenerates to singleton component
• can reduce the complexity of control
• can form a control hierarchy

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Overview of PERCO

• Two-tier hierarchical performance control
• CPS (Component Performance Steerer)
• one wrapped around each component
• all attached to APS (see below)
• maximises performance on deployed platform
• APS (Application Performance Steerer)
• (re)deploys components on available resources
• maximises performance on allocated platforms
• Requires an external resource allocator (from
  which to obtain a set of resources in which to
  effect its deployments)

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Modus Operandi

• Components progress via a sequence of progress
  points, at each of which a component calls out to
  its CPS for any component-specific performance
  control actions (local actuation requires
  component to be malleable)
• Certain progress points are also safe-points
  (i.e. the component is in a state that permits it
  to be redeployed) and, at these points, the CPS
  can call out to the APS for redeployment-based
  performance control actions (the APS means of
  actuation)

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Progress Points

• Assume that the execution of components and
  application proceeds through phases, and that the
  phase boundaries are marked by progress points.
• Can take decisions about performance and
  (possibly) actuate at the progress points

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Application vs. Component Progress Points
APS
Application progress points
CPS
Component progress points
Component
Time

• Application progress points need to be safe points

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PERCO System Overview
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PERCO Infrastructure

• Each component is attached to a local loader
  which is capable of moving the component safely
  around the distributed Grid hardware according to
  the APS commands
• The local loaders act in concert with the APS to
  form a virtual loader layer for the application
• Each CPS communicates with the local loader on
  behalf of its component

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PERCO System for 2 Components, C1 C2
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Controllable Components?

• Several groups have suggested that control should
  be effected via a component-based software
  architecture
• degenerates to singleton component
• can reduce the complexity of control
• can form a control hierarchy
• But where do the components come from?
• a knotty problem (cf. RealityGrid LB3D)

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One Answer . . .

• Homogeneous components
• each component a copy of the same model
• used e.g. for parameter search
• e.g. LB3D from RealityGrid
• Performance control scenarios
• N instances of LB3D, finish as fast as possible
• equates to keeping them in (approximate) timestep
  with each other (see next slides)
• execute N instances of LB3D at specified rates
  relative to one another
• e.g. N2, one instance executes twice as many
  timesteps per unit of time as the other

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With No Control
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With Control Exerted
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(No Transcript)
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Slightly More Complex Answer . . .

• Almost homogeneous components
• each component a copy of a similar model, but ...
• ... with different driving parameters
• e.g. LB3D with different resolutions
• Performance control scenarios
• TeraGyroid experiment (from RealityGrid
  conducted during SC2003 see next slide)
• IntBioSim beading method
• Hurricane tracking
• Embedded high resolution subdomains
• when does extra resolution become new physics?

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TeraGyroid Use Case Scenario
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Even More Complex Answer Coupled Models

• Many scientific modellers are finding a need to
  link together multiple models
• climate/envt. models (ocean atmosphere ...)
• multi-scale phenomena (CFD MD HybridMD)
• aircraft lightning strike (CEM a/f structure)
• others, all needing high performance Grid
• The individual models seem to constitute
  ready-made components
• can these be used for performance control?

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Summary

• We are investigating the practicalities of
  component-based performance control in Grid
  execution environments
• A prototype performance control system is being
  developed and we have shown that it can be used
  to achieve a scientifically meaningful high-level
  performance objective
• We are ready to apply it to realistic scientific
  coupled model applications
• K.R. Mayes, M. Luján, G.D. Riley, J. Chin, P.V.
  Coveney, J.R. Gurd, Towards performance control
  on the Grid, Philosophical Transactions of the
  Royal Society of London Series A, to appear,
  August 2005.

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Related Projects at Manchester

• FLUME - design of next generation Unified Model
  software
• funded by The Met Office (led by Mick Carter)
• RealityGrid condensed matter modelling
• EPSRC-funded e-Science (led by Peter Coveney at
  UCL)
• SoftIAM - climate impact, integrated assessment
  modelling
• funded by the Tyndall Centre (led by Rachel
  Warren)
• IntBioSim integrated biological simulation
• BBSRC-funded e-Science (led by Mark Sansom at
  Oxford)
• GENIEfy Earth system modelling
• NERC-funded e-Science (led by Tim Lenton
  Tyndall C)

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Weblinks

• For more information check
• http//www.cs.man.ac.uk/cnc
• http//www.realitygrid.org
• http//www.intbiosim.org (under construction)