CSC 714 ProjectsSpring 2009

P1: Pull Based Migration of Real-Time Tasks in Multi-Core Processors

Task

Migration

• Real-Time Scheduling on Multi-processors– Practical Schedulers

• Dynamic assignment of tasks to multi-cores• Fundamental Premise: tasks can migrate

• Problem– Task Migration causes cold cache misses

Temporal Guarantee in wake of Task Migration

Solution

• Scheduler has knowledge of– Task to migrate– Source and Target Cores

• Developer knows the critical memory regions– Combine the two into a prefetch thread

• Working– Scheduler spawns prefetch thread at target

• Prefetch thread has lowest priority

– Overlap prefetching with slack before next invocation

Simulation Results

• Matmult: – minor impact of task migration– Algorithmic complexity O(n3)

• CRC– Prefetch thread does not fill L1 I$– L1 Cache I$ misses significant

Impact of prefetch scheme

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Migration with prefetch

Prefetch Thread Overhead

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• CRC– Scattered Critical Regions– Additional prefetch function calls

Inferences• Cold Cache Misses can be hidden with prefetch scheme: Tighter bounds• Future Work: Memory layout may improve predicting the prefetch thread overhead

P2: Security Techniques in Cyber-Physical Systems

• Real-Time Systems Lack– Resources– Complex OS

• Failures can – Effect Environment– Effect Infrastructure– Harm Life

Real-Time Security Features

• Static Timing Analysis provides– WCET– BCET

• Predictable Scheduler Interupts – Check in on jobs

• Use timing data to bound regions of the running jobs– In Application– In Scheduler

Experiment

• Extend Current Research– Periodic Scheduler and Program

Instrumentation• Wide Granularity Checkpoints Fixed Distance

– Periodic Scheduler Orthogonal to Program• Arbitrary PC wakeup values must insure appropriate

pessimism

P3: Android Adhoc Wifi Networking

• Ad-hoc networking between G1 Android phones

• Social networking application– Text messages– Status updates– GPS coordinates

Solution: Adhoc Client Application• Borrow from Wifi-Tether Open Source project

– Init files, iptables, dnsmasq, tether script

• Discovery of other Ad-hoc endpoints– WifiManager not available– Alternate between DHCP Server/Client– UDP broadcast heartbeat messages

• Threads– UDP sender, UDP receiver, network control

• GUI Screens– Settings, Incoming Events, Friend List, My Status, Message View

• Tester program (runs on Laptop)– Echos back status message, GPS coordinates

Results• Successfully connected

2 phones in Ad-hoc mode– DHCP Server/ Client

• Also included an Access Point mode

• Laptop tester:

P4: CPU Shielding: Basics• Multi-core/Multi-processor Systems• Start with standard Linux• Partition CPUs between normal and

RT• Force all standard work to normal

CPUS• Use existing IRQ and Task affinities

• Project purpose: Demonstrate feasibility

CPU Shielding: Results

• Task affinities work, but are unenforceable• IRQ affinities don’t work as expected• Several IRQs must be per-CPU (ex. Local

timer, TLB helper)• Without kernel changes no useful

guarantees are possible• With kernel changes PCI bus speed

becomes the concern (single PCI port write takes up to 36 ㎲ on lab systems).

CPU Shielding: Future• Look at hiding CPUs & hardware via

hot-plug system• Kernel driver & structural changes to

implement scheduler for “off-line” CPUs

• Not a simple change. Worthwhile?• Security & Reliability of dual systems• Easier to implement using existing

virtualization methods?

• Limiting PCI latencies via ‘Latency Timer’

P5: Preemption Threshold aware Task-Scheduling Simulator

Term ProjectCSC714, April 2009

Sangyeol Kang, Kinjal Bhavsar

• Needs in design time– To help simulation of trial schedules– To support preemption threshold scheduling

• Implementation of timing simulator– RM, DM, EDF– Preemptive/Non Preemptive

• Supporting Preemption Threshold Scheduling– For fixed priority scheduling– Computing appropriate PT values using MPTA algorithm– Preempt only when “priority > PT of current running task”

• Graphical representation of simulated scheduling– By using third-party tool (gnuplot)

Motivation / Objectives

Results

Simulation StatisticsGraphical Representation

Task set & Parameters

P6: Fault Tolerant Algorithm for Multi Hop Wireless Sensor Networks

• Features• Rerouting capability on failure• Fault Tolerance through hardware redundancy• Isolation and self-recovery• Supports mobile sensor networks• Deployment of data mule to fetch/bridge isolated nodes.

• Built using Contiki OS and LNPD• Used Reliable Unicast protocol in Rime communication stack of

Contiki to mote-mote communicate• Used periodic broadcast for dynamic ad-hoc network formation.• LNPD is used for directing RCX data mule to bridge nodes• Used serial communication from mote to PC for instructing RCX

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Open Issues and Improvements

• Implementing the multi coordinator network

• Capability to place nodes using RCX

• The rover should be more sophisticated

•Investigate feasibility of implementation using

TCP/IP stack in Contiki

P7: Service Time Overlay for Google

MapsKarthikeyan Sivaraj

Mansoor Aftab

• An application to report average service times (waiting time)

• Users may like to know waiting times for banks, restaurants etc. beforehand– Helps user plan schedule better

• Accessible on a custom Google Maps overlay– User can navigate to the desired location and

click to know

• Data for service times is collected from the users phone

Introduction

• We use the Location(GPS) API provided in the Android SDK

• Client component implemented on user phones

– A background service reports location changes to server every minute

– Sends UDP messages with location and time spent

– MapView component to access service times

• Server component maintains database of locations and corresponding service times

– Implements various rules to decide validity of received data

– Responds to queries from the MapView component

Implementation

• Successfully implemented/tested the application with a distance resolution of 20m

• Provided user option to enable/disable background service

Results

P8: Save Gas Map

Problem description•To identify the shortest path for a given set of addresses and display them on the map

Team Members:Raghuveer RaghavendraPrasanna Jeevan

Implementation details Features

• Takes Input of multiple locations• Finds the shortest distance between all the

locations (Using a heuristic algorithm for TSP)

• Arranges the locations into a optimal route• Displays the location on Google map• Major classes used are Android Location,

Maps and Overlay

Snapshots

• Description: Design a PACMAN game using Lego-bots.

• Motivation: Design a simple system from scratch to study the interactions between the different units and design and timing complexities that are encountered.

• Aim: Pacman should traverse the entire maze while staying out of enemy’s way

P9:

• PACBOT and EnemyBots = line-followers + Messaging unit + Path-decision Logic

• Central Control = IR tower + messaging unit + display

• Issues:– Working of LNPD/Message setup– Path-decision algorithm– Timing– Orientation of RCX wrt the IR tower– Maze design

• Pacman needs to know enemy’s coordinates and direction

• Adjusted weights used for choosing direction

• Adjusted weight is a function of the numbers of untraversed cells in the direction and the presence/distance of enemy bots.

P10: Android WifiSocial Networking

Sushmita Lokala

Phil MarquisCSC714

Application• Read from disk

• Get location

• Get wifi status

• Send to server

• Receive from server

• Write to disk

• Draw map

• Draw overlays

Classes

• 1. Wifi

• WifiNetwork: SSID, Level

• WifiData: Latitude, Longitude, WifiNetworks

• WifiUserHistory: Name, WifiDatas

• 2. Maps

• WifiOverlay

Classes

• 3. Serialization: Disk

• ObjectOutputStream

• 4. Serialization: Server

• UDPServer

P11: A New Real-time Kernel development on an embedded platform

• Team

• BALASUBRAMANYA BHAT

• SANDEEP BUDANUR RAMANNA

CSC714: Real Time Systems Project – Spring 2009

Features

A new real-time kernel developed from scratch

Supports Periodic & Aperiodic tasks, Semaphores & Mutex

EDF based scheduling for periodic tasks (deadlines <= period)

The scheduler is capable of creating tasks based on (, p, e, D) parameters.

1 uSec granularity for all timing parameters (, p, e, D)

Aperiodic tasks are scheduled using static priority based preemptive scheduling.

The scheduler can also keep track of the current CPU utilization.

Design

Priority Queue based on the next DEADLINE

Ready Q

Wait Q

I

Aperiodic Q

Priority Queue based on the next RELEASE Time

Priority Queue based on task PRIORITY

Timer 0

Res. Block QPriority Queue based on Deadline / PRIORITY

Resource

Timer 1

Current StatusCompletedImplemented on C6713 DSK

TMS320C6713 DSP Processor VLIW Architecture (with 8 instructions / cycle)

Tested for all parameters (, p, e, D)Keeps track of Deadline miss & TBE counts for every threadAlso keeps track of thread wise execution time upto 1s res.About 2400 SLOCs of source code (1000 lines assembly)

Things to doOverall CPU utilization to be maintainedTest aperiodic tasks with resourcesImplement SleepFix few bugsTest with some real benchmarks

P12: MAC Protocol Implementation on Atmel AVR for

Underwater Communication

by Shaolin Peng

CSC 714 Real Time Computer Systems

Aloha Protocol

Atmega168

MACA Protocol

Small & Sparse Network

Small Packet Size

Development Platform:STK500

AVR Studio

Problem List• P1: Debugging Instrument

– Set up UART communication with the HyperTerminal on PC

– Connect two boards using wire as a start

• P2: Starvation– Wait only after sending, not after receiving

• P3: Flexible Length Packet Receiving– Receive the first two bytes, decode and decide

• P4: CRC Consideration– 4 bits -> 8 bits (x^8 + x^2 + x + 1)

Problem List 2• P5: Random Number Generator

– ADC or Timer Counter

• P6: No response problem– Set maximum retries number

• P7: Hardware Limitation– Compile different files using different optimization levels

• E.g. -O3 for Goertzel algorithm (critical path) -Os for the other files

Text data bss total

14986 302 141 15429 (different optimization levels)

16380 338 109 16827 (same optimization level)

Lake RaleighExperimental Setup

Throughput=Successfully received packets

Total packets sent out

Results

• Indoors– Aloha: 27.2%

– MACA: 23.8%

• Outdoors– Aloha: 8.1%

– MACA: 8.2%

• Compare with MACA– During the testing time, Aloha received almost twice

data than MACA

P13: Power-Aware DVFS on PowerPC 405LP: Front Bus Scaling➲ Mohamed Nishar Kamaruddin➲ Santhosh Selvaraj

➲ OVERVIEW➲ Previous work with the IBM 405LP board showed that

Feedback-DVS of the processor voltage and frequency produces considerable power savings.

➲ Our work is to study the frequency scaling for the memory subsystem to achieve power savings. We also study the feasibility of integrating this with the existing feedback DVS-EDF scheduling schemes.

Development up to present

➲ Experimented with different operating points including those with same processor frequency but with different memory subsystem frequencies. This was done on a number of applications.

➲ Changes to data acquisition programs and sample applications to record the power savings of the memory subsystem.

➲ Integration of PLB frequency scaling into the various existing feedback DVS-EDF scheduling schemes.

Results➲ Frequency scaling of the memory subsystem was found

to produce significant power savings. Reducing the FSB freq from 100MHz to 50 MHz for a tight noop looped application produced nearly 34% energy savings.

➲ Fitting this into the PID Feedback scheduling - we changed all operating points to use half of their original PLB frequencies. Energy savings now: 1.38%.

➲ This is because the various operating points defined in the PID feedback scheduling code already scale PLB frequency along with processor frequency.

➲ For memory intensive operation, energy savings: 1.1%