EXTRACTING FEATURE MODEL CHANGES FROM THE LINUX KERNEL WITH FMDIFF

The 8th International Workshop on Variability Modeling of Software-intensive Systems

Nicolas Dintzner Delft University of Technology

Netherlands N.J.R.Dintzner@tudelft.nl

Arie van Deursen Delft University of Technology

Netherlands Arie.vanDeursen@tudelft.nl

Martin Pinzger University of Klagenfurt

Austria martin.pinzger@aau.at

Linux kernel feature model changes

Feature changes

FMDiff

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Feature model changes

• Major changes in a S.P.L. are mirrored by changes in its feature model

• Details of the evolution of the Linux feature model are not available

• Can changes in a feature models can give insights on how the implementation changes ?

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Questions

1.  What types of changes can be applied to a FM ?

2.  How can we automate the extraction of feature changes

from a large scale FM?

3.  How does a large scale FM change over time ?

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Linux kernel • Very large feature model: 13k+ features

•  Long history: 20+ years of existence

•  Feature driven development: model “correctness”

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

A feature in a Kconfig file

if ACPI config ACPI_AC

tristate "AC Adapter" default y if ACPI depends X86 select POWER_SUPPLY help This driver supports the AC Adapter object ,(...).

endif

Name

Type & Prompt

Default

Depends

Select

(help text)

Additional structures

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Kconfig file

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Linux feature changes

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if ACPI config ACPI_AC

tristate "AC Adapter" default y if ACPI depends X86 select POWER_SUPPLY

endif

V1

if ACPI config ACPI_AC

boolean "AC Adapter” default y if ACPI default n if AIX depends X86 || AMD select POWER_SUPPLY

endif

V2

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Change classification

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Feature

Attribute Depends Default Select Add Remove Modify

Type Prompt

Expression References

Default value Condition References

Select Condition References

Add Remove Modify

Add Remove Modify Add Remove Modify Add Remove Modify

Add Remove Modify Add Remove Modify

Add Remove Modify

Add Remove Modify

CHANGE CATEGORY

CHANGE SUB-CATEGORY CHANGE TYPE

Classifying changes

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if ACPI config ACPI_AC

boolean "AC Adapter" default y if ACPI default n if AIX depends X86 || AMD select POWER_SUPPLY

endif

Rev. Feature Change type Change category

Change subcategory

Old value

New value

2 ACPI_AC Modification Change Attr. Change type “Tristate” “Boolean”

2 ACPI_AC Modification Add default Add default value n

2 ACPI_AC Modification Add default Add def. condition AIX

2 ACPI_AC Modification Modify depends Modify depends X86 X86||AMD

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

FMDiff: getting the changes

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Linux repository

Feature model translation

X86 v1

X86 v2

X86 v…

FMDiff

Feature model reconstruction (EMF)

Feature model comparison (EMF Compare)

Feature change classification

Feature change repository

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

From Kconfig to Kdump

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if ACPI config ACPI_AC

tristate "AC Adapter" default y if ACPI depends X86 select POWER_SUPPLY

endif

config ACPI_AC

tristate "AC Adapter" default y if ACPI depends X86 && ACPI select POWER_SUPPLY

1- Kconfig (original) 2- Hierarchy flattening

config ACPI_AC

tristate "AC Adapter" default y if X86 && ACPI depends X86 && ACPI select POWER_SUPPLY if X86 && ACPI

3- Depends propagation Item ACPI_AC tristate Prompt ACPI_AC 1 Default ACPI_AC "y" "X86 && ACPI" Depends ACPI_AC "X86 && ACPI" ItemSelects ACPI_AC POWER_SUPPLY "X86 && ACPI”

4- Kdump format (what we use)

Credits to for Undertaker and the translation process

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Rebuilding

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Kdump Feature Model

v1

Kdump Feature Model

v2

Feature model reconstruction (EMF)

Feature Model (Ecore)

EMF Feature

model Instance

v1

EMF Feature

model Instance

v2

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Meta model

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Feature

Type (string)Prompt (boolean)Depends (string)

DependsReferences (list of strings)

Select StatementTarget (string)

Condition (string)SelectConditionReferences (list of strings)

Default StatementDefaultValue (string)

Condition (string)DefaultValueReferences (list of strings)

DefaultValueConditionReferences (list of strings)

"contains"

"contains"

"contains"

FeatureModel

Architecture (string)Revision (string)

0*

0 *

0 *

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Example

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Item ACPI_AC tristate Depends ACPI_AC "X86 && ACPI" …

Item ACPI_AC tristate Depends ACPI_AC “(X86 || AMD) && ACPI" …

V1 V2

Feature Model Architecture: X86

Revision: 1

Feature Name: ACPI_AC

Depends: “X86 && ACPI” Depends references:

[X86,ACPI]

Feature Model Architecture: X86

Revision: 2

Feature Name: ACPI_AC

Depends: “(AMD || X86) && ACPI” Depends references:

[X86,ACPI,AMD]

Feature Meta-Model (Ecore)

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

EMF Compare

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Feature Model Architecture: X86

Revision: 1

Feature Name: ACPI_AC

Depends: “X86 && ACPI” Depends references:

[X86,ACPI]

Feature Model Architecture: X86

Revision: 2

Feature Name: ACPI_AC

Depends: “(AMD || X86) && ACPI” Depends references:

[X86,ACPI,AMD]

Mat

chin

g

Feature Model Architecture: X86

Revision: 1

Feature Model Architecture: X86

Revision: 2

Architecture Name

Feature Name: ACPI_AC

Depends: “X86 && ACPI” Depends references:

[X86,ACPI]

Feature Name: ACPI_AC

Depends: “(AMD || X86) && ACPI” Depends references:

[X86,ACPI,AMD]

Feature Name

Diff

eren

cing

Feature Model Architecture: X86

Attribute change: “Revision” “1”à“2”

Feature Name: ACPI_AC

Attribute change; “Depends”; “X86 && ACPI”à“(AMD||X8…” Attribute change; “Depends Ref.”; added “AMD”

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Feature model changes

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Feature Model Architecture: X86

Attribute change; “Revision”; 1 à 2

Feature Name: ACPI_AC

Attribute change; “Depends”; “X86 && ACPI” à “(AMD||X86) Attribute change; “Depends Ref”; added “AMD”

Rev. Feature Change type Change category

Change subcategory

Old value

New value

2 ACPI_AC Modification Modify depends modify depends X86 X86||AMD

2 ACPI_AC Modification Modify depends add depends ref. AMD

… … … … … … …

Feature change classification

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Linux kernel dataset •  10 releases (from v2.6.38 to v3.8)

•  Between 10,000 and 13,000 features in each release •  22 to 26 architectures •  Approximately 7000 feature per architecture specific F.M.

•  1,8+ million feature change recorded •  Tool and data available

•  https://github.com/NZR/Software-Product-Line-Research

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Add and remove

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

v2.6.39 v3.0 v3.1 v3.2 v3.3 v3.4 v3.5 v3.6 v3.7 v3.8

Perc

enta

ge o

f cha

nges

(arc

hite

ctur

e av

erag

e)

Linux releases

MODIFIED REMOVED ADDED

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

493 772 397 1740 612 493 750 609 1068 544

Spread over architectures (modifications)

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0

5

10

15

20

25

0 2 4 6 8 10

Series1

Series2

Series3

Series4

Series5

Series6

Series7

Series8

Series9

Series10

Series11

Series12

Series13

Series14

Series15

Series16

Series17

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

2.6.39 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8

Linux releases

num

ber o

f im

pact

ed a

rchi

tect

ures

5

10

15

20

25

Questions 1.  What types of changes can be applied to a FM ?

Change classification for Kconfig

2.  How can we automate the extraction of feature changes from a large scale FM?

We used Undertaker and EMF Compare 3.  How does a large scale SPL FM change over time ?

Dataset available…

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Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner

Extracting feature model changes from the Linux Kernel using FMDiff

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Modify Feature

Default

Modify

Add

CHANGE CATEGORY

CHANGE SUB-CATEGORY

CHANGE TYPE

Feature model change

Add Feature Remove Feature

Attribute

Add Remove Modify

Depends

Add Remove Modify Add Remove

Select

Add Remove Modify

Type Prompt

ExpressionReferences

Default ValueCondition

References

Add Remove Modify Add Remove Modify Remove Modify Add Remove Modify

Target Condition

References

Change Category

Change classification Tool and approach

Tool and dataset at your disposal Nicolas Dintzner

Pr. Arie Van Deursen Pr. Martin Pinzger

Contact: Nicolas Dintzner N.J.R.Dintzner@tudelft.nl

https://github.com/NZR/Software-Product-Line-Research

Extracting feature model changes from the Linux kernel with FMDiff - Nicolas Dintzner