1 asu mat 591: opportunities in industry performance modeling bo faser lockheed martin management...

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ASU MAT 591: Opportunities in Industry

Performance ModelingPerformance Modeling

Bo FaserLockheed Martin Management & Data Systems

Intelligence, Surveillance, and Reconnaissance SystemsLitchfield Park, Arizona

October 18, 2004

[email protected]

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Performance Modeling Overview Tool “Demonstration” System Model Examples Modeling Storage Systems Project Overview/Discussion

Topics

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Performance Modeling Overview

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Performance Modeling

What is it?– Performance modeling is a method of characterizing and

understanding system behavior in order to predict system performance. Generally refers to timeline performance.

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Why do we do it? – We use performance models to make good design decisions

Perform trade studies (processing power vs. bandwidth, disk storage vs. tape storage, microcoding vs. high level programming, vendor A vs. vendor B, everything vs. cost)

Find bottlenecks in the system (load balance) Predict performance of different input scenarios/test robustness

of system (sensitivity studies)– We use performance models to predict the effect of changes

to operational systems– Bottom line: We need to ensure that systems will satisfy

timeline performance requirements while taking into account system design constraints.

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Performance modeling is necessary in all program phases – Proposal Phase– Early Program Phase– Preliminary Design Phase– Detailed Design Phase

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Proposal Phase

In the proposal phase, performance modeling is used to estimate at a very high level the hardware required to meet the proposal requirements in order to develop the bid.– Roughly estimate the algorithm based on past work and

engineering estimates For example to calculate the number of compute strings:

calculate number of FLOPs (floating point operations) for the estimated number of FFTs in the algorithm, divide by the sustained FLOP rate of a known high performance computer scaled to future performance.

– This is generally done in a very short period of time in a spreadsheet.

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Early Program Phase

In the early part of a program, performance modeling is used to determine the right performance requirements to levy on the system.– Two ways to look at performance

Timelines for specific jobs (e.g., job type A needs to be done in 5 minutes)

Throughput of system (e.g., the system must be able to process 1000 job type A per day)

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Preliminary Design Phase

The focus of this discussion will be predominantly hardware (high performance computers, storage and communication)

Usually we have to begin hardware procurement long before we have a well defined algorithm.

We work with the algorithm group to determine the driving algorithm areas.– Within each area, we determine the driving algorithm

functions.– In Synthetic Aperture Radar (SAR) data processing, the

driver is usually a combination of FFTs and memory management.

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Develop Algorithm Processing Opscon– Determine the areas of the algorithm that are parallelizable.

Definition: In this discussion, a compute string or just a string is a high performance computer that has main memory and many processors (generally 8-256 processors per string).

Some functions are not parallelizable (for example: processing of a vector depends on the results of the previous vector).

Many functions are parallelizable but the communication required makes parallelization infeasible.

Interprocessor communication becoming less of a big deal as compute strings are designed with large main memory that can (theoretically) be accessed by every processor.

Inter-string communication is usually very slow and is therefore avoided.

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We need to refine our estimates from the proposal phase where we simply looked at FLOPs and determine clock cycles– Processors generally can perform more than one operation

per clock cycle (e.g., 4 multiplies and two adds may be performed simultaneously). Great! If the algorithm can exploit this.

– We need to determine how the algorithm can map to the various vendors’ processors.

– The modeling of this mapping is getting more difficult as vendors are using operation scheduling and doing out of order operations.

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Now you have string processing time. We can do that in a spreadsheet.

– There is a lot more to the system latency than just string processing time.

To understand the performance of the system, we need to look at the interaction of the jobs in the system to understand and design for resource contention (queues).

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Example Architecture

DS1

RAID

RAID RAID

CAR

MDC1 MDC3

MDC2

FIBRESW

FIBRESW

WIC

WIC

DS2

PC

CS

4GE

4FC4

GE

4FC

100 MB/s ea.

100 MB/s ea.

400 MB/s

400 MB/s

400 MB/s

400 MB/s

100 MB/s

100 MB/s

100 MB/s

2.2 GB/s

80 MB/s

80 MB/s

RDB2

RDB1

UDA/PDB

.. ..

.... ..[66 TB/9 TB]

4FC

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Timeline Performance Models

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The type of models that we are talking about are:– Dynamic: Represents system as it changes over time– Stochastic: Has components that are subject to chance– Discrete Event: State of system changes instantaneously at

the times that events occur

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Discrete event simulation modeling could theoretically be done by hand

Example:– The system:

1 Compute String Interrarrival times of jobs are exponentially distributed with

mean 2 minutes Service Times are exponentially distributed with mean 1 minute

– We want to know average latency for a job (time it takes to get through the system) We will run the simulation through the first three jobs


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Let interarrival times and service times for first three jobs be

The event list

A1 A2 A3 S1 S2 S3

2.3 1.5 1.1 0.3 1.4 0.5

t= 0 Initialization Processor = idle Qlength=0t= 2.3 Job 1 arrives t= 2.3 Job 1 enters service Processor = busy

t= 2.6 Job 1 completes service Processor = idle Latency1= 0.3

t= 3.8 Job 2 arrives t= 3.8 Job 2 enters service Processor = busyt= 4.9 Job 3 arrives Qlength=1


t= 5.2 Job 3 enters service Processor = busy Qlength=0


Avg. Latency = 0.83


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Generally the systems are too complex and the number of events that we want to observe are too many to do the modeling by hand so we develop computer program simulations (models)


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What does a performance model need?– Main Program to execute model including initialization routine and

output report generator

– Event List

– Simulation Clock

– Routines for advancing clock,executing events, and generating random variables

– Storage for state variables and statistics (things you want to measure)

Performance modeling can be done in any programming language but there are packages specifically designed to take care of the bookkeeping for us.


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Tool “Demonstration”

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There are numerous commercial off the shelf modeling packages available– We use Hyperformix Workbench

Discrete Event Simulation Package built on C code Not particular to any industry modeling (very powerful) GUI interface

High level models can be built very quickly Models are easy to understand

Models can be run in “animate” mode Useful for explanation/demonstration Useful for debug/test

Models can be complied into executable code that can be run on platform without Workbench tool

Provides easy interface statistics gathering and reporting

COTS Modeling Packages

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SES Workbench ModelMain Module

Dependence Arc

Create modules under model tab

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SES Workbench Model

sub models

NodePalette

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SES Workbench Model

source node

service node

sink node

declarationnode

Response arc (gathers stats)

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SES Workbench Model

Exponentially dist. mean 2

Can track statistics fordifferent job types

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SES Workbench Model

Queuing discipline

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SES Workbench Model

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SES Workbench Model

Right click on module to get specification

Module time unit

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SES Workbench Model

Will run until no events on event list or 100 minutes (sim time)Whichever is less

Will give status every 10 minutes (sim time)

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SES Workbench Model

Reports status at report interval

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SES Workbench ModelMM1_model.rpt file reports all statistics that have been gathered

Output from response arc

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System Model Examples

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What kind of systems do we model?

Complex End to End Systems Compute Intensive/Data Intensive

DataCapture

DataStorage

DataProcessing

DataArchive

DataDistribution

Functional Block Diagram

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ASU MAT 591: Opportunities in IndustryWhat kind of questions are we trying to answer?

How many compute servers do we need to meet our timeline requirements?

What is the processor utilization? What is the average wait in the processor queue? What is the average wait in the output queue? What is the maximum amount of bandwidth the disk needs to provide? What is the optimal compute server configuration? Should we overlap I/O and processing? What is the 90th percentile for end-to-end latency? How much working memory do I need on my processors? How much data should I leave on disk/tape? Which algorithm will run the fastest?

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Modeling Process

Performance Requirements

Candidate Hardware/Software Specifications

Design Constraints System Usage Scenario System Operational

Concept

Timeline Performance Predictions

Utilization Predictions

Performance Model

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The Marketing Pitch

By doing detailed performance modeling you WILL:

Have a tool for determining the best operating concept Have a tool for determining the best operating concept for your systemfor your system

Have the ability to “try before you buy”Have the ability to “try before you buy”

Give your customers peace of mind that their Give your customers peace of mind that their complex system will meet its requirements.complex system will meet its requirements.

Avoid buying more bandwidth than you needAvoid buying more bandwidth than you need

Avoid buying more hardware than you needAvoid buying more hardware than you need

Avoidmaking

stupid decisions

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Why is modeling a cool job?

Understand the system from end to end– Breadth not necessarily depth knowledge

Can influence architecture design and opscon design Get to “see” the system performance before the system is operational Get to work with the latest HPC technology.

1 asu mat 591: opportunities in industry performance modeling bo faser lockheed martin management...

Documents

system performance

performance models

performance timelines

future performance

asu mat

right performance requirements

industry proposal phase

modeling storage systems