ChooJeongHo/gradle-build-performance

Gradle Build Performance

Analyze and optimize build performance for $ARGUMENTS (or run a full audit if no argument given).

Quick Wins (check these first)

1. Configuration Cache

# Check current status
./gradlew assembleDebug --configuration-cache

# Enable permanently in gradle.properties
org.gradle.configuration-cache=true
org.gradle.configuration-cache.problems=warn  # start with warn, move to fail later

Benefit: Skips configuration phase on subsequent builds (30-60% faster incremental builds). Gotcha: Some plugins don't support it yet — check output for incompatibilities.

2. Parallel Execution

# gradle.properties
org.gradle.parallel=true
org.gradle.workers.max=4  # adjust to CPU core count - 1

3. Daemon & Memory

# gradle.properties
org.gradle.daemon=true
org.gradle.jvmargs=-Xmx4g -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8

4. Build Cache

org.gradle.caching=true

AGP 9 Specific

# Already required for this project — verify present
android.disallowKotlinSourceSets=false
android.enableR8.fullMode=true

# AGP 9 non-transitive R classes (faster builds, less R class bloat)
android.nonTransitiveRClass=true

# Disable unused features
android.defaults.buildfeatures.buildconfig=false  # only enable per-module if needed
android.defaults.buildfeatures.aidl=false
android.defaults.buildfeatures.renderscript=false

KSP vs KAPT

This project uses KSP (already). Verify no KAPT stragglers:

# Should return nothing
grep -r "kapt" app/build.gradle.kts

KSP is ~2x faster than KAPT. Never mix both for the same processor.

Profile a Slow Build

# Generate build scan (detailed task timeline)
./gradlew assembleDebug --scan

# Or local profile report
./gradlew assembleDebug --profile
# Report: build/reports/profile/

# Check which tasks are slowest
./gradlew assembleDebug --info 2>&1 | grep "Task.*took"

Common Slow Tasks & Fixes

| Slow Task | Cause | Fix | |-----------|-------|-----| | kspDebugKotlin | Large annotation processing | Split into modules (future) | | testDebugUnitTest | All tests always re-run | --tests filter for local dev | | detekt | Full source scan | Run only on changed files (CI) | | jacocoTestReport | Instrument + report | Run only on CI, not local | | lint | Full lint pass | ./gradlew lintDebug only when needed | | packageDebug | Large assets | Check for accidentally committed large files |

Incremental Build Health

# Run twice — second should be UP-TO-DATE for most tasks
./gradlew assembleDebug
./gradlew assembleDebug

# If tasks re-run on second build, they're not incremental
# Common culprit: task reads System.currentTimeMillis() or non-deterministic input

Module-Level Optimization (future)

If build time exceeds 3 min, consider splitting:

:core        (pure Kotlin — fastest to compile)
:data        (Room, Retrofit)
:domain      (pure Kotlin UseCases)
:app         (presentation only)

Benefit: only changed modules recompile. Currently single-module is fine for this project size.

Detekt Performance

# Run only on app module source, not test sources
./gradlew :app:detekt

# Already configured in this project — verify source.setFrom() in build.gradle.kts

Pre-push Hook Optimization

Current hook runs full testDebugUnitTest. If it's too slow:

# Option: run only affected module tests
./gradlew :app:testDebugUnitTest --daemon --quiet

# Option: parallel test execution (already default in AGP 9)
# Verify in build.gradle.kts:
testOptions {
    unitTests.isParallelized = true  // add if not present
}

Audit Output Format

## Build Performance Audit

### Current Baseline
- Clean build: Xs
- Incremental build: Xs
- Test only: Xs

### Configuration Cache Status
[Enabled/Disabled + any incompatible plugins]

### gradle.properties Gaps
[Missing optimizations vs recommended settings]

### Top 5 Slowest Tasks
[Task name → time → fix recommendation]

### Quick Win Priority
1. [Highest impact, lowest effort]
2. ...

### Estimated Improvement
[X% faster incremental builds after applying recommendations]