context-specific middleware specialization techniques for optimizing software product-line...

Context-Specific Middleware Context-Specific Middleware Specialization Techniques for Specialization Techniques for

Optimizing Software Product-line Optimizing Software Product-line ArchitecturesArchitectures

Arvind S. Krishna, Aniruddha S. Gokhale, Douglas C. SchmidtInstitute for Software Integrated Systems, Dept of EECS

Vanderbilt University Nashville, TN, USA

Venkatesh P. Ranganath, John HatcliffDept of Computer and Information Sciences

Kansas State UnivManhattan, KS, USA

Eurosys’06, Leuven, BelgiumApril 18-21, 2006

2

F-15productvariant

A/V 8-Bproductvariant

F/A 18productvariant UCAV

productvariant

Product-line architecture

Hardware (CPU, Memory, I/O)Hardware (CPU, Memory, I/O)

OS & Network ProtocolsOS & Network Protocols

Host Infrastructure MiddlewareHost Infrastructure Middleware

Distribution MiddlewareDistribution Middleware

Common Middleware ServicesCommon Middleware Services

Middleware for Product Line Architectures

•Middleware factors out many reusable general-purpose & domain-specific services from traditional DRE application responsibility

•Essential for product-line architectures (PLAs)

• e.g., Boeing Boldstroke Avionics mission computing PLA for Boeing fighter aircrafts (F-15, F/A-18, AV-8B, UCAV/JUCAS)

• DRE system with 100+ developers, 3,000+ software components, 3-5 million lines of C++

• Used as open experimentation platform

AirFrame

AP

NavHUD GPS

IFF

FLIR

Domain-specific ServicesDomain-specific Services

3

F-15productvariant



productvariant









•However, standards-based, general-purpose, layered middleware is not yet adequate for the most demanding & mission-critical PLA-based DRE systems

AirFrame

AP

NavHUD GPS

IFF

FLIR



4

F-15productvariant



productvariant




Specialized MiddlewareSpecialized Middleware



•However, standards-based, general-purpose, layers middleware is not yet adequate for the most demanding & mission-critical PLA based DRE systems

AirFrame

AP

NavHUD GPS

IFF

FLIR

Soln: Middleware Specialization for PLA-based DRE systems


5

Middleware Specialization Evaluation Criteria

Premise

• Application of specialization techniques should result in considerable improvements in QoS over & above horizontal general-purpose middleware optimizations

• Handcrafting specializations infeasible for large-scale DRE systems => need for tools and processes

• Specializations should have minimal impact on standards compliance (APIs)

Evaluation Criteria

• Use TAO (www.dre.vanderbilt.edu/TAO) as gold standard with several general-purpose optimizations

• Set performance improvements ~30 to 40% improvement from application of specializations cumulatively

• Turning on just one/two optimizations might improve performance by ~10 to 15%

6

Opportunities for Middleware Specialization

Container

ClientOBJREF

in argsoperation()out args +

return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter

ORB CORE GIOP/IIOP/ESIOPS

Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

1

2

3

• Certain functionality can be excessive for PLAs• e.g., layered demultiplexing, leading to

unnecessary performance overhead

• Challenge: automatically remove specification-imposed generality when it’s not needed

• Goal is to devise techniques that apply to any standards compliant middleware, not just an implementation

• Dimension #1: Specification-imposed generality

• Standards-based general purpose middleware functionality defined by specifications such as CORBA, J2EE etc

4

7

Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

• Dimension #2: Middleware framework generality

• General-purpose middleware implementations need to work across applications that have varying functional & QoS requirements

• Accommodate variability by providing hooks

• e.g., for different protocol, concurrency & demultiplexing strategies• Hooks add overhead indirections & dynamic dispatching

• PLAs however require one alternative; one protocol

TCP/IP, VME, SCTP, SHMIOP

Thread-pool, Single-threaded, Thread-

per connection

• Challenge: Automatically specialize middleware frameworks to eliminate unnecessary hooks

• Goal is devise techniques applicable to distributed systems that apply common patterns


8


Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

• Dimension #3: Platform generality

• Middleware implementations run on different hardware/OS/compiler platforms

• Platforms provide certain optimizations that can be leveraged to enhance QoS

gcc 3.2 (no exceptions),

timesys kernel

Green-hills compiler, vxWorks

platform

• Challenge: Automatically discover PLA deployment platform characteristics to improve QoS

• Goal is to devise techniques that apply to any host infrastructure middleware (e.g., ACE or JVMs) targeting heterogeneous OS, compiler, & hardware platforms

9

Bold Stroke PLA ScenarioExample PLA configuration: Basic Single Processor (BasicSP) – DRE system scenario based on Boeing Bold Stroke challenge problems from DARPA PCES & MoBIES

ACE_wrappers/TAO/CIAO/DAnCE/examples/BasicSPCoSMIC/examples/BasicSP

Goal: Select representative DRE system, e.g., “rate based” events for control information & operations that transmit common data

• Timer Component – Triggers periodic refresh rates

• GPS Component – Generates periodic position updates

• Airframe Component – Processes input from the GPS component & feeds to Navigation display

• Navigation Display – Displays GPS position updates

TIMER20H

z

GPS NAV DISPAIRFRAME

TIMER

20Hz


timeout data_avail

get_data ()

data_avail

get_data ()

10

Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Services

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

Identifying “Ahead of Time” System Invariants

A specific Reactor used

Protocol: A specific protocol

used

Specification Invariance

Framework Invariance Deployment Invariance

Does not support native exceptions

TIMER20H

z


TIMER

20Hz


timeout data_avail

get_data ()

data_avail

get_data ()Single method

interfaces:Sends same operation on

wire

14

Feature Oriented CUStomizer (FOCUS)

Middleware Instrumentation Phase

Middleware Specialization Phase

FOCUS addresses specialization challenges by building specialization language, tool, & process to capture & automate middleware specializations

Application Devloper

Ruleselection

OS & Network ProtocolsOS & Network ProtocolsOS & Network ProtocolsOS & Network Protocols

Customized MiddlewareCustomized MiddlewareCustomized MiddlewareCustomized Middleware

AP

NavHUD GPS

IFF

FLIR

• ~1,000 Perl SLOC Parser + weaver

• ~2,500 XML SLOC specialization files

• ~50 (files) annotations

SplRules

Foo (){ ….. ……. //hook …}

Middleware Developer

•Capture specialization transformations via FOCUS specialization language

•Annotate middleware source code with specialization directives

•Create a domain-specific language (DSL) to capture middleware variability

•Analyses & determines the type of specializations applicable

•FOCUS transformation engine selects the appropriate transformations & uses the annotations to automate specializations

16

Specialization Experimental Setup

Goals

• Application of specialization techniques should result in considerable improvements in QoS over & above horizontal general-purpose middleware optimizations

TAO baseline• Active demultiplexing & perfect hashing

for O(1) request demultiplexing• Buffer caching & direct collocation

optimization• Optimized configuration for different

ORB components

Experiment Setup• Pentium III 850 Mhz processor,

running Linux Timesys 2.4.7 kernel, 512 MB of main memory, TAO version 1.4.7 compiled with gcc 3.2.3

• Timers at the client & within ORB used to collect data

• Used Emulab testbed

Specialized TAO Middleware

17

Results for Layer-folding Specialization

Average end-to-end measures improved by ~16%

Average path measures improved by ~40%

Worst case path

measure improved by ~20%

Worst case end-to-end

latency improved by

~14%• Path specialized latency measures

• Path defined as code-path when a request is received until the upcall is dispatched on the skeleton

Experiment

• End-to-end latency measures for:

• General-purpose optimized TAO with active demultiplexing & perfect hashing

• Specialized TAO with layer folding specialization enabled

Specialization applied at the server side (can also be applied at the client side)

Dim #1: Specification Imposed generality

Dim #2: Framework generality

Dim #3: Deployment generality

Dispersion improves by a factor of ~1.5 for both cases

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Cumulative Specialization Results

Worst-case measures

improved by ~45%

• End-to-end client side throughput improved by ~65%. • Results exceeded the hypothesis & evaluation criteria

• Specification related• Layer folding• Memoization• Constant propagation

(ignoring endianess)• Framework• Aspect weaving

(Reactor + protocol)• Deployment • Loop unrolling +

emulated exceptions

Average end-to-end measures

improved by ~43%

Jitter results twice as good as general-purpose optimized TAO

Layer folding, deployment platform,

memoization, constant propagation

21

Evaluating FOCUS Pros & ConsStrengths• Provides a lightweight, zero (run-time)

overhead middleware specialization• Designed to work across different

languages (e.g., Java & C++)• KSU applying FOCUS &

specializations to Java ORBs• XML-based rule capture

• Easy language extension, ability to add new features easily

• If/when C++ aspect technologies mature, can transform them into aspect rules via XSLT transforms

• Execute transformations via scripting• Integration with QA tools; code

generation from models

Drawbacks

• Doesn’t provide full-fledged language parser, i.e., join points identified via annotations or via regular expressions

• Need to synchronize annotations with specialization files, so modifying source code requires change to specialization files

• Ameliorated via distributed continuous QA; Limitation exists even with aspects

• Correctness of transformations have to be validated externally; unlike AspectJ

• Need higher level tools to validate combinations of specializations

FOCUS available in latest ACE+TAO distribution in ACE_wrappers/bin/FOCUS

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Future Work System Optimizations

• FOCUS approach applied to middleware optimizations

Model-Driven Technologies

Domain-Specific Modeling Languages

• Future work will focus on identifying system level (middleware, platform, application) specializations

• Goal is to drive the specialization process to optimize systems layer-to-layer

• Capturing invariants in models and using generative technologies to drive specializations

• Other QoS parameters

25

F-15productvariant



productvariant


Concluding RemarksResolving the tension between•Generality Middleware is designed to be independent of particular application requirements

•Specificity PLAs are driven by the functional & QoS requirements for each product variant (using SCV analysis)

Specialized Middleware Stack







•Domain-specific language (DSL) tools & process for automating the specializations

•Development of reusable specialization patterns

•Identifying specialization points in middleware where patterns are applicable

•Latency improvements of 45%

•www.dre.vanderbilt.edu

QUESTIONS ?

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FOCUS Research Goals

SplRules

Foo (){ ….. ……. //hook …}

Middleware Developer

• Contributions: The goal of this work isn’t on specialization languages per se, but instead to quantify the improvements that come from applying various types of specializations to middleware

• Transformational approaches: Stratego-XT, DMS support a broader range of specializations

Application Devloper

Ruleselection

OS & Network ProtocolsOS & Network ProtocolsOS & Network ProtocolsOS & Network Protocols

Customized MiddlewareCustomized MiddlewareCustomized MiddlewareCustomized Middleware

AP

NavHUD GPS

IFF

FLIR

Domain specific language for capturing

specializations; minimize accidental complexity

Process to support specialization with evolution

Language agnostic; leverage

annotations

Ensuring transformations (1) do not incur additional

overhead; (2) do not compromise portability

Develop a process that enables role

separation

Applying specializations improve latency

~30 – 40%

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FOCUS Specialization Phase

//File: Reactor.h

//@@ REACTOR_SPL_INCLUDE_HOOK// Code woven by FOCUS:#include "ace/Select_Reactor.h"// END Code woven by FOCUSclass Reactor{public: int run_reactor_event_loop (); // Other public methods ....private: // Code woven by FOCUS: ACE_Select_Reactor *reactor_impl_; // End Code woven by FOCUS // ......};

//File: Reactor.h//@@ REACTOR_SPL_INCLUDE_HOOKclass Reactor{public: virtual int run_reactor_event_loop (); // Other public methods ....private: ACE_Reactor_Impl *reactor_impl_; // ......};

Annotated middleware source Transformed middleware source

• These specializations don’t affect framework “business logic,” just its structure• Existing framework is still available when developers need OO capabilities

Removed virtual keyword

Replaced ACE_Reactor_Impl with ACE_Select_Reactor

#include concrete header file

Annotations help identify join points

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Automating Layer Folding Specialization




<add> <hook>TAO_DISPATCH_OPT_ADD_HOOK</hook> <data> 1. if (__dispatch_resolved__) 2.{ 3: //First invocation normal path 4: __dispatch_resolved_ = 1; 5: } 6: else 7:{ // All invocations go through --- Optimized path 8: this->request_disaptcher__.dispatch (…) 9:} <data></add>

Normal path; the dispatch is cached

in the process

Directly use cached dispatcher

Component Source Files {h,cpp} (loc) FOCUS Specialization file

Layer folding

Demultiplexing (tao, PortableServer)

• tao/GIOP_Base 1,200• PortableServer/Servant_Base 2,000

• <add>, <substitute>, <comment>• Specialization file ~250 loc• Tag related changes (5 locations) in

TAO & Portable Server

Automating Specialization via FOCUS•On a per connection basis determine the target dispatcher; •For subsequent requests, directly use the dispatcher to process requests

FOCUS enables specification of specializations in corresponding

language syntax

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Automating Reactor Specialization


Aspect Weaving

Reactor Framework (ACE, TAO modules)

• ace/Reactor 1,500• ace/Reactor_Base 1,800 • ace/Select_Reactor 2,500• tao/advanced_resouces 2,500

• <add>, <substitute>, <copy-from-source> <comment>

• Specialization file ~700 loc• Tag related changes (10 locations) <

0.1% of the code within the Reactor framework

Automating Specialization via FOCUS

• <substitute>,<add>: weave code that creates specialized Reactor

• <copy-from-source> to move implementation from Select_Reactor to base Reactor component

• <comment>: comment unspecialized code

<add> <hook>TAO_REACTOR_SPL_COMMENT_HOOK_END</hook> <data> ACE_NEW_RETURN (impl, ACE_Select_REACTOR (….), 0); </data>

ACE_Reactor_Impl *TAO_Advanced_Resource_Factory::allocate_reactor_impl (void) const{ ACE_Reactor_Impl *impl = 0;//@@ TAO_REACTOR_SPL_COMMENT_HOOK_START switch (this->reactor_type_) { ………… }//@@ TAO_REACTOR_SPL_COMMENT_HOOK_END}

Transformations preserve hooks;

Minimizes clutter in middleware source




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Automating Platform Specializations

Deployment platform specialization• Exception support:

• Autoconf’s AC_COMPILE_IF_ELSE macro to check if compiler supports native exception

• Loop unrolling optimization• Autoconf’s AC_RUN_IF_ELSE macros to compile & run benchmark to quantify memcpy() performance improvements

ACE_CACHE_CHECK([if ACE memcpy needs loop unrolling], [ace_cv_memcpy_loop_unroll],[AC_RUN_IFELSE([AC_LANG_SOURCE([[ /// …. Program that will run the benchmark to //// determine if an optimization is better

Variable that will be checked to set a compilation flag

Directive to run the benchmark

Provide actual source

language that will be compiled &

run

This approach can be applied automatically to discover OS-specific system calls & compiler settings that maximize QoS


Constant Propagation

(autoconf)

• ace/CDR_Stream 4,000• ace/Message_Block 2,000

• Code changes ~650• Benchmark ~250




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Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Services

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

Concluding Remarks

•Domain-specific language (DSL) tools & process for automating the specializations

Specification-imposed specializations• Layer-folding• Constant propagation• Memoization

Framework specializations• Aspect Weaving

techniques• Bridge Reactor• Template method

Protocol• Strategy Messaging,

Wait, Demultiplexing

Deployment platform specializations• Unroll copy loops • Use emulated exceptions• Leverage zero-copy

data transfer buffers

•Development of reusable specialization patterns

•Identifying specialization points in middleware where patterns are applicable

35

Foo (){ ….. ……. //hook …}

ACE_Reactor_Impl *TAO_Advanced_Resource_Factory::allocate_reactor_impl (void) const{ ACE_Reactor_Impl *impl = 0;//@@ TAO_REACTOR_SPL_COMMENT_HOOK_START switch (this->reactor_type_) { ………… }//@@ TAO_REACTOR_SPL_COMMENT_HOOK_END}

Middleware Annotations• Middleware developer

annotates middleware with hooks• Hooks represented as

“meta-comments,” i.e., opaque to compilers

FOCUS Instrumentation Phase

<?xml version='1.0'?> <transform>11: <module="TAO/tao">12: <file name="advanced_resource.cpp">13: <comment>14: <start-hook>TAO_REACTOR_SPL_COMMENT_HOOK_START </start-hook>15: <end-hook>TAO_REACTOR_SPL_COMMENT_HOOK_END </end-hook>16: </comment>17: </file>18: </module>23: .... </transform>

Annotations help identify join points & relieve

FOCUS from Implementing a full

fledged language parser

36

Lessons Learned (2/2)Specializations have potential to improve task schedulability

•Specializations help high priority tasks finish ahead of their time to complete• Tasks with priority 50 finish early,

increasing time available for scheduling priorities with 35 & 10

•Specializations can benefit both hard real-time & soft & softer real-time tasks

Adaptation with specializations can adversely affect QoS•Specializations do not consider any form of recovery if invariance assumptions fail

•Adaptation requires loading general-purpose code, add checks along request processing path; increases jitter for DRE systems

QoS improvements are scenario specific•All our specializations improve path latencies considerably than end-to-end latency; More the specialized code path is traversed, greater is QoS improvement

Thread Pool with Lanes

PRIORITY

35PRIORITY

50PRIORITY

10

POA

S1 S2

POA

S320

S435

POA

S540

S550

Specializations increase slack in

the system

37

Applicability of Specialization Approaches

Resolving Specification Imposed Generality•Applicable to standards compliant CORBA middleware

•Layer folding specialization CORBA demultiplexing; Other layered demultiplexing approaches




•Avoiding (de)marshaling checks middleware standards such as J2EE, .NET that target heterogeneous deployment

Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

1

2

3

4

Big endian

Little endian

38





Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

TCP/IP, VME, SCTP, SHMIOP

Thread-pool, Single-threaded, Thread-

per connection

Resolving Framework generality Specialize design pattern

Reactor Framework specialization Bridge patternProtocol framework specialization Template method pattern

•Techniques to distributed systems that apply these patterns (www.dre.vanderbilt.edu/POSA)

39





Container

ClientOBJREF


return

IDLSTUBS

ORBINTERFACE

IDLSKEL

Object Adapter


Component(Servant)

Se

rvic

es

ProtocolInterface

ComponentInterface

ServicesInterface

DII

DSI

Green-hills compiler, vxWorks

platform

gcc 3.2 (no exceptions),

timesys kernel

Dimension #3: Resolving Deployment generality•Host Infrastructure middleware (ACE, JVMs) targeting heterogeneous OS, compiler & hardware characteristics •Systems concerned with QoS

context-specific middleware specialization techniques for optimizing software product-line...

Documents

product variant av

b product variant fa

layered middleware

layers middleware

generalpurpose optimizations

largescale dre systems

application of specializations

ucavjucas dre system