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Intelligent Offloading

Strategies for COMET

Ajit Aluri

Silky AroraSupriya Rao

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Contents

Introduction to COMET

Scheduling in COMET

Our Approach

Intelligent Code Offload Infrastructure and Results

Conclusions and Future Work

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Introduction to COMET

Extends DalvikVM to freely migrate threads between end

points using distributed shared memory (DSM) at the

granularity of fields.

Uses VM synchronization primitives to maintain a consistent

state between the end points

Supports multiple threads by using lazy release consistency.

Prior work: CloneCloud, JMM, Jessica

DSMDSM

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END POINT 1 END POINT 2

Bar()

Foo()

Foo()

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Scheduling in COMET

=syncCount lastSyncTime + 1 syncCount RTT

10

okTime = currTime lastUnsafePoint

Offload when okTime >

okTime represents the time since the last native method

execution

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Our Approach

COMET currently focuses on howto offload as compared to

whento offload

Our Goal - Improve the offloading decision engine of COMET

using the following

Incorporating bandwidth in the scheduling decision

Static Analysis of applications

Dynamic profiling to get method execution times

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Static Analysis

WALA profiler for generating call graphs for an application

Helps in identification of native methods and their parents

0

2

4

6

8

10

12

ProportionofNativeMethods(%) % of Native Methods

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Dalvik Debug Monitor Server (DDMS) for dynamic profiling

Helps in identifying methods that run a significant amount of

time before calling a native method

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60

ExecutionTimet

oNativeMethod(uS)

Parent Methods

com.adobe.psmobile

com.wimolife.fractal

com.magmamobile.game.checkers

Dynamic Analysis

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Native-to-NextNative

Execution time Heuristic

Parent-to-NativeExecution

time Heuristic

Intelligent Code Offload

Parent Pa

Native Na

t1

Parent Pa

Native Na

Native Nb

t2

t3

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Infrastructure

Server cairo.eecs.umich.edu

o 8 core Intel i7 with 3.40 Ghz processor and 32 GB RAM

Client - Samsung Galaxy Nexuso Cyanogenmod 10.0 tc enabled kernel

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Results

0

5

10

15

20

25

30

35

40

0.51 0.91 2 5 7 9

Executiontimeinsec

Bandwidth in Mbits/sec

Intelligent Offload

Baseline COMET

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Results

100

105

110

115

120

125

130

0.51 0.91 2 5 7 9

ExecutionTimeinsec

Bandwidth in Mbits/sec

Intelligent Offload

Baseline COMET

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Results

Iterations BaselineCOMET IntelligentOffload % Improvement

5 36.6 33 10%

10 45.67 41.33 9.5%

15 60 48 20%25 71.6 51 28.7%

50 112.67 102 9.5%

100 188 179 4.8%

Performance improvement of 4.5% for com.adobe.psmobile applicationusing Heuristic 1 (Parent-to-Native)

Results for further experiments on synthetic application at 900Kbps forHeuristic 2 (Native-to-NextNative):

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Future Work

Include the methods of interest inside the applications

executable

Compute last execution time of methods of interest without

relying on DDMS

Cleaner way to recover from aborting the sync based on

bandwidth measurements

Improve the calculation of last sync time

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Thank You!