Performance and Extensibility with EMF

Getting the Most out of Your Models
Performance and Extensibility with EMF

Dave Steinberg, IBM
Marcelo Paternostro, IBM
Kenn Hussey, Committerati

Thursday, March 25, 2010 © IBM Corp., Committerati Consulting Corporation | EPL v1.0 1

Exercise Prerequisites
• USB drives are being passed around
– Separate images for 64-bit and 32-bit platforms
– Copy the contents to a temporary location and pass it on
• Extract platform-appropriate eclipse-SDK-3.6M6-*.zip to some
location
– Do not nest deeply on Windows
• Launch Eclipse and use Help > Install New Software... to install
the modeling features
– Add a local site, and specify the modeling-projects/ subfolder of the
temporary location
– Install all the features from the site
– Accept installation of unsigned software
– Restart the workbench
• Import all of the projects from emf-tutorial-workspace.zip

Thursday, March 25, 2010 © IBM Corp., Committerati Consulting Corporation | EPL v1.0
2

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Validation delegates
– Setting delegates
– Invocation delegates
– Exercise
• Q&A

3

As you already know...
• EMF is the foundation for modeling and data
integration at Eclipse
• Ecore models describe types of objects, their
attributes, operations, and relationships
– Extensible import support including UML, XML Schema, and
annotated Java interfaces
• Merging generator enables mixing of generated and
hand-written code
• Runtime framework provides notiﬁcation, reﬂective
API, dynamic EMF, XML persistence, validation...

4

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

5

Balancing Performance

Speed Memory

6

Balancing Performance

Speed Memory

7

Measuring Performance
• Measuring performance in Java is tricky
• Speed
– What are you measuring? (inlining, JIT, garbage collection, etc.)
– Precision was a big problem for small operations, until Java 5
added System.nanoTime()

• Memory
– What are you measuring? (deep size, shared objects, static ﬁelds,
etc.)
– No way to estimate the size of a given object until Java 5 added
Instrumentation.getObjectSize()

• Comparisons are useful, single measurements not
so much
8

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

9

EObject Overhead
public class EObjectImpl ... 32 bytes
{
protected int eFlags; // deliver, dynamic, proxy
protected BasicEList<Adapter> eAdapters; EAdapterList
protected InternalEObject eContainer; ≥ 32 bytes
protected int eContainerFeatureID;
protected EPropertiesHolder eProperties;
...
}

protected static class EPropertiesHolderImpl ... 32 bytes
{
protected EClass eClass;
protected Resource.Internal eResource;
protected Object[] eSettings; EContentsEList
protected URI eProxyURI; ≥ 24 bytes
protected EList<EObject> eContents;
protected EList<EObject> eCrossReferences;
... ECrossReferenceEList
} ≥ 24 bytes

A fully ﬂuffed up (but empty) instance has 144 bytes of overhead!

10

Alternative EObject Implementations
• DynamicEObjectImpl moves eSettings and
eClass out of properties holder

• FlatEObjectImpl moves eProxyURI, eContents,
and eCrossReferences out of properties holder

11

“EMF Ultra Slim Diet”
• MinimalEObjectImpl uses a different approach:
– Dynamically sized array (or single object) for all overhead
– Does not cache contents or cross references
– Adapters stored as array or simply delegated to container

public class MinimalEObjectImpl ...
{
private int eFlags;
private Object eStorage;
...

public static class Container extends MinimalEObjectImpl
{
protected InternalEObject eContainer;
...
}
}

• Overhead of empty, ﬂuffed up
MinimalEObjectImpl.Container instance is just 24 bytes
12

Modeled Features
public class ProjectImpl
extends EObjectImpl
implements Project
{
...

protected ProjectPhase phase = PHASE_EDEFAULT;
protected boolean ipClean = IP_CLEAN_EDEFAULT; 4 bytes
protected boolean inSimultaneousRelease =
IN_SIMULTANEOUS_RELEASE_EDEFAULT;
... 1 byte
public ProjectPhase getPhase() {
return phase;
}

public boolean isIpClean() {
return ipClean;
}

...
}

13

Boolean Flags & Packed Enums
public class ProjectImpl extends EObjectImpl implements Project
{
...
protected int flags = 0;
protected static final int PHASE_EFLAG_OFFSET = 0;
protected static final int PHASE_EFLAG = 0x3 << PHASE_EFLAG_OFFSET;
private static final ProjectPhase[] PHASE_EFLAG_VALUES =
ProjectPhase.values();
protected static final int IP_CLEAN_EFLAG = 1 << 2;
protected static final int IN_SIMULTANEOUS_RELEASE_EFLAG = 1 << 3;
...

return PHASE_EFLAG_VALUES[
(flags & PHASE_EFLAG) >>> PHASE_EFLAG_OFFSET];
}

public boolean isIpClean() {
return (flags & IP_CLEAN_EFLAG) != 0;
}
...
}

14

Boolean Flags & Packed Enums
• Unset states also recorded in flags field
• Reduces size by up to 87.5% for booleans

• Can leverage protected eFlags field in
EObjectImpl (not MinimalEObjectImpl), but 8
bits must be reserved

15

Virtual Delegation
public class ProjectImpl extends EObjectImpl
implements Project
{
...
protected Object[] eVirtualValues;
protected int eVirtualIndexBits0;

protected Object[] eVirtualValues() {
return eVirtualValues;
}
...

return (ProjectPhase)eVirtualGet(
FoundationPackage.PROJECT__PHASE, PHASE_EDEFAULT);
}
...
}

16

Virtual Delegation
• Appropriate only for very sparsely populated models
with many features – measure before adopting!

17

Reﬂective Method Dispatch

public class TopLevelProjectImpl
extends ProjectImpl
implements TopLevelProject
{
...

public Object eGet(int featureID, boolean resolve, boolean coreType)
{
switch (featureID) {
case FoundationPackage.TOP_LEVEL_PROJECT__PROJECTS:
return getProjects();
case FoundationPackage.TOP_LEVEL_PROJECT__PMC_MEMBERS:
return getPmcMembers();
}
return super.eGet(featureID, resolve, coreType);
}
...
}

18

O(1) Reﬂective Methods
public class TopLevelProjectImpl extends ProjectImpl
implements TopLevelProject
{
...
public Object eGet(int featureID, boolean resolve, boolean coreType)
{
switch (featureID) {
case FoundationPackage.TOP_LEVEL_PROJECT__PHASE:
return getPhase();
case FoundationPackage.TOP_LEVEL_PROJECT__IP_CLEAN:
return isIpClean();
case FoundationPackage.TOP_LEVEL_PROJECT__IN_SIMULTANEOUS_RELEASE:
return isInSimultaneousRelease();
case FoundationPackage.TOP_LEVEL_PROJECT__PROJECTS:
return getProjects();
case FoundationPackage.TOP_LEVEL_PROJECT__PMC_MEMBERS:
return getPmcMembers();
}
return eDynamicGet(featureID, resolve, coreType);
}
...
}

19

O(1) Reﬂective Methods
• Performance improvement possible only for deep inheritance
hierarchies
• Trade-offs are memory impact of duplicated code (not heap)
and cross-model inheritance fragility (need to regenerate)

• Note: default reﬂective dispatch is not binary compatible

20

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

21

Identifying EObjects in Resources
• Fragment paths
– The default, a slash-delimited path computed based on
containment within the resource
– For multi-valued features, segments can be based simply on an
index or on values of one or more “key” attributes
• Intrinsic IDs
– Used when an EObject's EClass deﬁnes an “ID” attribute and that
attribute is set
• Extrinsic IDs (XML resources only)
– Used only when an EObject is explicitly assigned an ID
– Particular resource implementations may do this automatically

22

Extrinsic IDs
• EObject-Extrinisic ID associations are recorded in
two maps (one for each direction)

XMLResource xmlResource = ...
Project project = ...
xmlResource.setID(project, "EMF-Project-123");
xmlResource.getContents().add(project);

assert project == xmlResource.getEObject("EMF-Project-123");
assert "EMF-Project-123" == xmlResource.getID(project);

• These maps are maintained by the XMLResource
and should not be manipulated directly

23

Extrinsic IDs
• Serialized via xmi:id or xsi:id attributes
• UUIDs can be automatically assigned by the
resource

public class MyXMLResourceImpl extends XMLResourceImpl
{
@Override
protected boolean useUUIDs() {
return true;
}
}

• Note: a single UUID consumes 88 bytes!

24

Intrinsic IDs
• An EObject's intrinsic IDs is part of its state
– The string value of the EAttribute that is deﬁned to be the ID of
the EClass

Resource resource = ...
Project emf = (Project)resource.getEObject("EMF");
assert FoundationPackage.Literals.PROJECT__NAME.isID();
assert "EMF".equals(project.getName());

• Finding an EObject by intrinsic ID involves walking
over the entire resource

25

“Secret” Caches
• It is possible to improve performance by using some
lesser known caches:
– Intrinsic ID to EObject (in Resource)
– URI to Resource (in ResourceSet)

• Both caches
– can be pre-populated
– are lazily populated as elements are retrieved

26

Intrinsic ID to EObject Cache
Resource resource = ...

Map<String, EObject> cache = new HashMap<String, EObject>();
((ResourceImpl)resource).setIntrinsicIDToEObjectMap(cache);

Project project = ...
project.setName("EMF");
assert FoundationPackage.Literals.PROJECT__NAME.isID();

resource.getContents().add(project);

• Heads up:
– EObjects that are removed from the resource are automatically
removed from the cache
– EObjects with non-null intrinsic IDs that are added to the
resource are automatically added to the cache
– The cache may become inconsistent (e.g. if an EObject's intrinsic
ID is changed after it has been added to the resource)
27

URI to Resource Cache
• Obtaining the resource for a URI can be expensive,
especially if it involves URI normalization
ResourceSet resourceSet = ...

Map<URI, Resource> cache = new HashMap<URI, Resource>();
((ResourceSetImpl)resourceSet).setURIResourceMap(cache);

• Heads up:
– Resources that are removed from the resource set are automatically
removed from the cache
– The cache may become inconsistent (e.g. if a resource's URI is
changed)
– URIs in the cache (key values) don't include fragments

28

Intrinsic ID Performance

29

Large Resource Performance

30

Cross-Resource Containment
• Cross-resource containment allows an object
hierarchy to be persisted across multiple resources
– eObject.eResource() may be different from
eObject.eContainer().eResource()

• Side beneﬁt: facilitates ﬁner-grained partial loading

31

Cross-Resource Containment
EClass TopLevelProjectEClass = ...
EClass projectEClass = ...

EReference projects = EcoreFactory.eINSTANCE.createEReference();
Dynamic projects.setName("projects");
Model projects.setUpperBound(ETypedElement.UNBOUNDED_MULTIPLICITY);
projects.setEType(projectEClass);
projects.setContainment(true);
projects.setResolveProxies(true);
topLevelProjectEClass.getEStructuralFeatures().add(projects);

Generated
Model

32

Binary Resources
• EMF also supports a high-performance proprietary
binary serialization format
– Numeric IDs for EObjects, metadata, URIs
– String lengths speciﬁed, no delimiters
– Signature to recognize corruption
– Versioned to allow for future format changes

33

Binary Resources

34

Binary Resource
Resource.Factory binaryResourceFactory = new Resource.Factory()
{
public Resource createResource(URI uri) {
return new BinaryResourceImpl(uri);
}
};

ResourceSet resourceSet = new ResourceSetImpl();
resourceSet.getResourceFactoryRegistry().
getExtensionToFactoryMap().put("dat", binaryResourceFactory);
Resource resource = resourceSet.createResource(
URI.createFileURI("projects.dat"));

35

Save and Load Options
• Resource implementations offer a set of options that
can be used to tweak load and save behavior
• Options passed to the resource’s save and load
methods as entries in a map
– Key: the constant that represents the option
– Value: appropriately typed for the option

36

XMLResource xmlResource = ...

Map<String, Object> options = new HashMap<String, Object>();
options.put(Resource.OPTION_ZIP, true);
options.put(XMLResource.OPTION_USE_PARSER_POOL,
new XMLParserPoolImpl());
options.put(XMLResource.OPTION_USE_CACHED_LOOKUP_TABLE,
new ArrayList<Object>());
xmlResource.save(options);

• Options are usually declared in
– resource interface (e.g. XMLResource)
– resource implementation class (e.g. BinaryResourceImpl)

• Get used to opening the EMF source code or
Javadoc to read about them

37


38

A Nod to Scalability: CDO
• Connected Data Objects (CDO): an EMF component
offering central persistence for models and
instances
– Multiple clients can have views on and transactions against a
single remote repository
– Clients may modify the shared object graph concurrently
– Other clients are immediately notiﬁed about modiﬁcations
• Supports CDO-targeted generated models, dynamic
models, and “legacy” models
• The way forward for truly scalable EMF
– Pluggable DB storage (Derby, MySQL, HSQLDB, etc.)
– Full demand loading and unloading of objects, with partial
collection loading and adaptable pre-fetching
39

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

40

Exercise
• Have Fun!
– The goal for the next few minutes is to let you
experiment with EMF
– Use the knowledge you've learned during the
tutorial so far:
• Try saving and loading resources using
different options
• See the difference between different types of
resources (XMI and binary for example)
• Re-generate the model using different
genmodel settings
41

Sample Model

42

Cheat Sheet: Test Harness
• In project org.eclipsecon.foundation.test:
– ModelFactory
• Creates instances of the Foundation model
• The number of instances can be controlled by constructor
arguments
– MemoryTester
• Outputs the size of the instances of the model
• Requires the “-javaagent” JVM argument
– ResourceTester
• Base class for classes that time saving and loading resources

43

Cheat Sheet: Resource Options
• org.eclipse.emf.ecore.resource.Resource
– OPTION_ZIP
– OPTION_SAVE_ONLY_IF_CHANGED
• OPTION_SAVE_ONLY_IF_CHANGED_MEMORY_BUFFER
• OPTION_SAVE_ONLY_IF_CHANGED_FILE_BUFFER
• org.eclipse.emf.ecore.resource.impl.BinaryResourceImpl
– OPTION_BUFFER_CAPACITY

44

Cheat Sheet: XML Resource
• Load
– OPTION_DEFER_IDREF_RESOLUTION
– OPTION_USE_PARSER_POOL
– OPTION_USE_XML_NAME_TO_FEATURE_MAP
– OPTION_USE_DEPRECATED_METHODS
• Save
– OPTION_FLUSH_THRESHOLD
– OPTION_CONFIGURATION_CACHE
– OPTION_FORMATTED
– OPTION_USE_FILE_BUFFER
– OPTION_USE_CACHED_LOOKUP_TABLE

45

Exercise 1
Performance


Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

47

Extensibility
• Many enhancements have been made to EMF over
the past few years to make the framework more
extensible

• As of the M4 milestone of the Helios release, EMF
has been made even more extensible with the
addition of support for validation, feature setting,
and operation invocation delegation

• We'll consider each of these new mechanisms in
turn and look at how they can be implemented and
used for our sample model
48

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

49

Validation Delegation
• The EMF Validation Framework previously supported
evaluation of invariants and constraints, deﬁned
as methods and implemented in Java, via a validator
that is invoked at important moments by an
application or at a user’s discretion

• In order to delegate evaluation of invariants and
constraints to an external engine, the framework
was enhanced by introducing the concept of a
validation delegate

50

Implementing Validation Delegates
• Deﬁne a validation delegate by implementing the
ValidationDelegate interface

• Register the validation delegate, either
programmatically or via an extension

51

Using Validation Delegates
• Reference the validation delegate via an annotation
on an Ecore package

• Define the behaviors of invariants and/or
constraints via expressions in annotations on Ecore
operations and/or classifiers

• Evaluate invariants and/or constraints, either
statically via generated code or dynamically via EMF
reflection

52

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

53

Feature Setting Delegation
• EMF previously supported computation of features,
deﬁned as methods and implemented in Java, via an
API that is invoked at important moments by an
application

• In order to delegate computation of a feature’s
value to an external engine, the framework was
enhanced by exposing the previously existing
concept of a setting delegate

54

Implementing Setting Delegates
• Deﬁne a setting delegate by implementing the
SettingDelegate interface

• Deﬁne a setting delegate factory by implementing
the Factory interface

• Register the setting delegate factory, either

55

Using Setting Delegates
• Reference the setting delegate factory via an
annotation on an Ecore package

• Deﬁne the values of features via expressions in
annotations on Ecore structural features

• Compute the values of features, either statically via
generated code or dynamically via EMF reﬂection

56

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

57

Operation Invocation Delegation
• EMF previously supported execution of operations,
deﬁned as methods and implemented in Java, via an
API that is invoked at important moments by an
application

• In order to delegate execution of an operation’s
behavior to an external engine, the framework has
been enhanced by introducing the concept of an
invocation delegate

58

Implementing Invocation Delegates
• Deﬁne an invocation delegate by implementing the
InvocationDelegate interface

• Deﬁne an invocation delegate factory by
implementing the Factory interface

• Register the invocation delegate factory, either

59

Using Invocation Delegates
• Reference the invocation delegate factory via an
annotation on an Ecore package

• Deﬁne the values of operations via expressions in
annotations on Ecore operations

• Execute the behaviors of operations, either
statically via generated code or dynamically via EMF
reﬂection

60

Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

61

Exercise 2
Extensibility


Agenda
• Introduction
• Performance
– Generated code
– Resources
– Exercise
• Extensibility
– Exercise
• Q&A

63

Questions?


Resources
• Online help
– http://help.eclipse.org/ganymede/index.jsp?nav=/14
• Website
– http://www.eclipse.org/emf
• Downloads
• Wiki
• FAQ
• Newsgroup
• Documentation

• Book
– Eclipse Modeling Framework
• Second Edition
– http://safari.awprofessional.com/9780321331885

65

Legal Notices
Copyright © IBM Corp. and Committerati Consulting Corporation, 2010. All rights reserved.
This presentation and the source code in it are made available under the EPL, v1.0.
Java and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United
States, other countries, or both.
Eclipse and the Eclipse logo are trademarks of Eclipse Foundation, Inc.
IBM and the IBM logo are trademarks or registered trademarks of IBM Corporation, in the
United States, other countries or both.
UML and XMI are registered trademarks of the Object Management Group.
HTTP, Metadata, and XML are trademarks of the World Wide Web Consortium; marks of W3C
are registered and held by its host institutions MIT, ERCIM, and Keio.
Other company, product, or service names may be trademarks or service marks of others.

THE INFORMATION DISCUSSED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL
PURPOSES ONLY. WHILE EFFORTS WERE MADE TO VERIFY THE COMPLETENESS AND ACCURACY
OF THE INFORMATION, IT IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, AND IBM SHALL NOT BE RESPONSIBLE FOR ANY DAMAGES ARISING OUT OF THE
USE OF, OR OTHERWISE RELATED TO, SUCH INFORMATION. ANY INFORMATION CONCERNING
IBM'S PRODUCT PLANS OR STRATEGY IS SUBJECT TO CHANGE BY IBM WITHOUT NOTICE.

66

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