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Relevance of code
minification in a
performance world
Jitin Sharma
GDE Android, Gojek
Android Worldwide jitinsharma.com
@_jitinsharma
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What we’ll
discuss
• Code obfuscation and minification
• Introduction to obfuscation tools
• Proguard rules
• Performance impacts of code
minification
• Common mistakes and how to avoid
them
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Obfuscation
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Life of code
Kotlin Class dex
Source code Bytecode Bytecode
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Life of code
Kotlin Class dex
Source code Bytecode
resources
+
apk
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Life of code
Kotlin Class dex
Source code Bytecode Bytecode
• dedexer
• smali
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Life of code
Kotlin Class dex
Source code Bytecode Bytecode
jadx
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Obfuscation
class Repository
viewModel.fetchData()
fun matchUser()
val loggedIn = false
package com.awesome.app
class a
c.zz()
fun rt()
val y = false
package com.g.f
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minification
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Minification
fun main() {
fetchUser()
}
fun fetchUser() {
fetchProfile()
}
fun fetchProfile() {
displayProfile()
}
fun displayProfile() { .. }
main()
fetchUser()
fetchProfile()
displayProfile()
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Minification
fun main() {
fetchUser()
}
fun fetchUser() {
// fetchProfile()
}
fun fetchProfile() {
displayProfile()
}
fun displayProfile() { .. }
main()
fetchUser()
fetchProfile()
displayProfile()
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Minification
fun main() {
fetchUser()
}
fun fetchUser() {
// fetchProfile()
}
fun fetchProfile() {
displayProfile()
}
fun displayProfile() { .. }
main()
fetchUser()
fetchProfile()
displayProfile()
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Minification
Activities Service Application Receivers
Code
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Minification
Activities Service Application Receivers
Code resources
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Tools
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Proguard
Dexguard
R8
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Android Toolchain
Code
(source code + libraries)
Obfuscation
+ minification
D8/R8
minified
dex AGP Toolchain
(removes unused
resources)
manifest,
resources
apk
dex/IR
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Android Toolchain
Code
(source code + libraries)
dex/IR
minified
dex AGP Toolchain
(removes unused
resources)
manifest,
resources
ResourceUsageAnalyzer.java
apk
Obfuscation
+ minification
D8/R8
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Rules
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Rules
fun main() {
val clazz = Class.forName()
val method = clazz.getDeclaredMethod()
method.invoke()
}
main()
method()
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Rules
fun main() {
val clazz = Class.forName()
val method = clazz.getMethod()
method.invoke()
}
main()
method()
Classes Fields Interfaces Functions
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Rules
- keep class …
- keepclassmembers …
- keep attributes …
- dontwarn …
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Optimisation and Performance
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Test bed project
~20 modules, 100 classes, 6000 methods
androidx Rxjava Glide Kotlin
AGP 4.1 D8/R8
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Comparison
App Type Size App Launch Mode
Non Minified 11.8MB 596.6ms Release
Minified 6.5MB 367.9ms Release
Minified + Shrinked 6.4MB 361.3ms Release
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11.8 mb
596.6 ms
6.4 mb (45%)
361.3 ms (39%)
Non Minified
Minified
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Optimisations
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Code Inlining
fun myBranchedFunction() {
if (BuildConfig.DEBUG) {
debugMethod()
} else {
releaseMethod()
}
}
fun myBranchedFunction() {
releaseMethod()
}
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Code Inlining
fun myBranchedFunction() {
releaseMethod()
}
fun main() {
myBranchedFunction()
myFunction2()
}
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Code Inlining
fun myBranchedFunction() {
releaseMethod()
}
fun main() {
releaseMethod()
myFunction2()
}
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Code Inlining
if (Build.VERSION.SDK_INT >= 21) {
window.statusBarColor = ..
}
if (Build.VERSION.SDK_INT >= 28) {
val displayCutOut = decorView.rootWindowInsets.displayCutout
...
}
minSdk 19
if (Build.VERSION.SDK_INT >= 21) {
window.statusBarColor = ..
}
if (Build.VERSION.SDK_INT >= 28) {
val displayCutOut = decorView.rootWindowInsets.displayCutout
...
}
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Code Inlining
if (Build.VERSION.SDK_INT >= 21) {
window.statusBarColor = ..
}
if (Build.VERSION.SDK_INT >= 28) {
val displayCutOut = decorView.rootWindowInsets.displayCutout
...
}
minSdk 21
window.statusBarColor = ..
if (Build.VERSION.SDK_INT >= 28) {
val displayCutOut = decorView.rootWindowInsets.displayCutout
...
}
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Code Inlining
if (Build.VERSION.SDK_INT >= 21) {
window.statusBarColor = ..
}
if (Build.VERSION.SDK_INT >= 28) {
val displayCutOut = decorView.rootWindowInsets.displayCutout
...
}
minSdk 28
window.statusBarColor = .. val displayCutOut = decorView.rootWindowInsets.displayCutout
...
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Code Inlining
fun trim(String name) {
Intrinsics.checkParameterIsNotNull(name)
name(…)
}
fun trim(String name) {
if (name != null) {
name(…)
} else { // exception }
}
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App Startup
596.6 ms 361.3 ms (39%)
Non Minified
Minified
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App Startup
Non Minified
Minified
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App Startup
Non Minified
Minified
Dex load: 2.96 ms
Dex load: 0.07 ms
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Systrace Event Non minified Minified Mode
bindApplication 54.46 ms 19.24 ms Release
ResourcesManager#getRes
ources
4.62 ms 3.97 ms Release
ResourcesImpl#updateCon
figuration
3.98 ms 2.62 ms Release
LoadApkAssets 1.3 ms 0.68 ms Release
VectorDrawable#inflate 0.41 ms 0.39 ms Release
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Rules
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Rules can hurt you
- keep class com.mypackage.**
- keep com.somepackage.R$*
- keepclassmembers enum * {
public static **[] values();
public static ** valueOf(java.lang.String);
}
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Case Study
keepclassmembers class **.R$* {
public static ;
}
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Transitive R classes
App
Module1
Module2
Module3
Module4
Module5
aar
aar
aar
aar
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Transitive R classes
App
Module1
Module2
Module3
Module4
Module5
aar
aar
aar
aar
R.class
R.class
R.class
R.class
R.class
R.class
R.class
R.class
R.class
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11.8 mb
596.6 ms
6.4 mb (45%)
361.3 ms (39%)
Non Minified
Minified
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6.4 mb
361.3 ms
Minified
6.6 mb (+3%)
487.1 ms (+34%)
Minified with faulty rules
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6.4 mb
361.3 ms
Minified
6.6 mb (+3%)
487.1 ms (+34%)
Minified with faulty rules
Dex Count: 1
Dex Size: 634KB
Dex load: 0.07ms
Dex Count: 2
Dex Size: 894KB
Dex load: 0.09ms
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Rules
• Be aggressive instead of defensive when defining proguard rules.
• Avoid wildcard package rules.
• Use @Keep to attach rules to codebase instead of rules files.
• Scan for rules which third party rules are importing in your codebase.
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Imported Rules
proguard-rules.pro
-printconfiguration
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Imported Rules
proguard-rules.pro
-printconfiguration
build/outputs/mapping/release/configuration.txt
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Further Optimisations
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
proguardFiles getDefaultProguardFile(‘proguard-android-optimize.txt’), 'proguard-rules.pro'
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Further Optimisations
gradle.properties
android.enableR8.fullMode=true
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Debugging Rules
-addconfigurationdebugging
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Proguard Playground
https://playground.proguard.com/
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No content
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Further Reading
• https://developer.android.com/studio/build/shrink-code
• https://www.zacsweers.dev/android-proguard-rules/
• https://jakewharton.com/blog (Search for R8 optimization)
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Thanks
@_jitinsharma