Towards Elastic Operating SystemsAmit GuptaEhab AbabnehRichard HanEric Keller

University of Colorado,Boulder

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OS/Process

Resources Limited• Thrashing• CPUs limited• I/O bottlenecks

• Network• Storage

Present Workarounds• Additional Scripting/Code changes• Extra Modules/Frameworks

• Coordination• Synch/Aggregating State

OS + Cloud Today

ELB/CloudMgr

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Advantages• Expands available Memory • Extends the scope of Multithreaded

Parallelism (More CPUs available)• Mitigates I/O bottlenecks• Network• Storage

Stretch ProcessOS/Process

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ElasticOS : Our Vision

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ElasticOS: Our Goals “Elasticity” as an OS Service

Elasticize all resources – Memory,CPU, Network, …

Single machine abstraction Apps unaware whether they’re running on

1 machine or 1000 machines Simpler Parallelism

Compatible with an existing OS (e.g Linux, …)

6“Stretched” Process Unified Address Space

OS/Process

V R

Elastic Page TableLocation

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Movable Execution ContextOS/Process

• OS handles elasticity – Apps don’t change• Partition locality across multiple nodes• Useful for single (and multiple) threads

• For multiple threads, seamlessly exploit network I/O and CPU parallelism

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Replicate Code, Partition Data

CODE

Data 1

Data 2

CODE CODE

• Unique copy of data (unlike DSM)• Execution context follows data

(unlike Process Migration, SSI )

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Exploiting Elastic Locality• We need an adaptive page clustering

algorithm• LRU, NSWAP i.e “always pull”• Execution follows data i.e “always

jump”• Hybrid (Initial): Pull pages, then Jump

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Status and Future Work Complete our initial prototype Improve our page placement

algorithm Improve context jump efficiency Investigate Fault Tolerance issues

Thank YouQuestions

?

Contact:amit.gupta@colorado.edu

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Algorithm Performance(1)

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Algorithm Performance(2)

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Page PlacementMultinode Adaptive LRU

CPUs

Mem

Swap CPUs Swap

Mem

Pulls Threshold Reached !Pull First

JumpExecution

Context

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Locality in a Single Thread

CPUs

Mem

Swap CPUs Swap

Mem

Temporal Locality

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Locality across Multiple Threads

CPUs

Mem

Swap CPUs Swap

Mem

CPUs Swap

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Unlike DSM…

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Exploiting Elastic Locality• Assumptions • Replicate Code Pages, Place Data Pages

(vs DSM)• We need an adaptive page clustering

algorithm• LRU, NSWAP• Us (Initial): Pull pages, then Jump

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Replicate Code, Distribute Data

CODE

Data 1

Data 2

CODE CODE

• Unique copy of data (vs DSM)• Execution context follows data

(vs Process Migration)

AccessingData 1 Accessing

Data 2Accessing

Data 1

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Benefits OS handles elasticity – Apps don’t

change Partition locality across multiple nodes

Useful for single (and multiple) threads For multiple threads, seamlessly

exploit network I/O and CPU parallelism

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Benefits (delete) OS handles elasticity

Application ideally runs unmodified Application is naturally partitioned …

By Page Access locality By seamlessly exploiting multithreaded

parallelism By intelligent page placement

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How should we place pages ?

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Execution Context JumpingA single thread example

Address Space

Node 1

Address Space

Node 2

Process

TIME

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Address Space

Node 1

Address Space

Node 2

Process

V RPage Table

IP Addr

“Stretch” a Process Unified Address Space

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Operating Systems Today Resource Limit = 1 Node

OS

CPUs

Mem

Disks Process

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Cloud Applications at Scale

Cloud Manager

LoadBalancer

Process

More Resources ?

ProcessProcess

Framework (eg. Map Reduce)

Partitioned Data

Partitioned Data

Partitioned Data

More Queries ?

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Our findings Important Tradeoff

Data Page Pulls Vs Execution Context Jumps

Latency cost is realistic Our Algorithm: Worst case scenario

“always pull” == NSWAP marginal improvements

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Advantages Natural Groupings: Threads &

Pages Align resources with inherent

parallelism Leverage existing mechanisms

for synchronization

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“Stretch” a Process : Unified Address Space

V R

CPUs

Mem

Swap

CPUs

Mem

Swap

Page Table

A “Stretched” Process =

Collection of Pages + Other Resources { Across Several Machines }

IP Addr

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delete Exec. context follows Data Replicate Code Pages

Read-Only => No Consistency burden Smartly distribute Data Pages Execution context can jump

Moves towards data *Converse also allowed*

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Elasticity in Cloud Apps Today

D1

~~~~

~~~~

~~~~

Input Data

….~~~

~~~~

~~~~

~

CPUs

Mem

Disk

Output Data

D2 Dx

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D1

Load Balancer

….~~~

~~~~

~~~~

~

CPUs

Mem

Disk

Output Data

D2 Dx

Input Queries

Dy

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(delete)Goals : Elasticity dimensions Extend Elasticity to

Memory CPU I/O

Network Storage

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Thank You

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Bang Head Here !

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Stretching a Thread

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Overlapping Elastic Processes

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*Code Follows Data*

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Application Locality

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Possible Animation?

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Multinode Adaptive LRU

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Possible Animation?

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Open Topics Fault tolerance

Stack handling

Dynamic Linked Libraries Locking

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Elastic Page TableVirtual Addr

Phy. Addr Valid Node (IP addr)

A B 1 LocalhostC D 0 LocalhostE F 1 128.138.60.

1G H 0 128.138.60.

1

Local MemSwap spaceRemote Mem

RemoteSwap

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“Stretch” a Process Move beyond resource boundaries of

ONE machine CPU Memory Network, I/O

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D1 D2

~~~~

~~~~

~~~~

Input Data

….~~~

~~~~

~~~~

~

CPUs

Mem

Disk

Output Data

CPUs

Mem

Disk

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D1

CPUs

Mem

Disk

D2

CPUs

Mem

Disk

~~~~

~~~~

~~~~

Data

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Reinventing Elasticity Wheel