jvmperf

JVM (Java / Kotlin) performance notes, runnable examples, JMH/JOL benches, and jvmperf-lint written in Java.

Part of XPerf. Shared docs: docs/README.md. Corpus-ready. Small evidence JSONL lives under evidence/.

ContentsCopy Anchor Link

• English guide — from docs/guide-src/en/
• jvmperf-lint — Java checker (Gradle, tree-sitter)
• Corpus pins
• Evidence pointers · evidence-policy
• HotSpot correlate: scripts/run-static-vs-hotspot.sh

FocusCopy Anchor Link

Allocation / boxing, layout (SoA, primitive maps), hot-path strings & I/O, JIT/false-sharing/virtual threads, Kotlin sequences & inline. Claims without a local bench or citation stay provisional; corpus counts are lint dogfood.

RequirementsCopy Anchor Link

• JDK 21 to build and test jvmperf-lint (CI: Temurin 21). Pin JAVA_HOME to 21 — a host JDK 25 alone can make Gradle fail with an opaque 25.0.x message. The project uses a Java 21 toolchain + Foojay resolver.
• JDK 25 optional for JMH/JOL examples and benches (separate JAVA_HOME when running those scripts)
• Kotlin 2.4.x for Kotlin examples (scripts/check_kotlin.sh)
• Optional jars in lib/ — not in git; bash scripts/fetch-lib.sh (see lib/README.md). Default JVMPERF_LIB_DIR=$ROOT/lib

Run lintCopy Anchor Link

cd packages/jvmperf/jvmperf-lint
export JAVA_HOME="${JAVA_HOME:-/usr/lib/jvm/java-21-openjdk-amd64}"
./gradlew test jar
bin/jvmperf-lint ../examples --no-fail
bin/jvmperf-lint --list-rules

Exit code 1 when findings exist (unless --no-fail). Exit 2 on usage/IO errors.

Severity note: process exit still treats any finding as failure unless --no-fail. Each rule's default severity (error, hint, or off) follows docs/evidence-policy.md; rules marked off do not run unless selected with --enable (which then runs only the listed rules). Full --preset wiring may land later.

Self-check: ./gradlew test (fixtures + unit). Dogfood examples with --no-fail as review prompts.

Benches & checksCopy Anchor Link

# From packages/jvmperf: rebuild guides from docs/guide-src (code samples are inlined in the chapter files)
bash ../../scripts/build-guides.sh jvmperf
scripts/check_java.sh
scripts/check_kotlin.sh
# JMH / JOL / Kotlin alloc (writes JSONL under research/bench-results):
# scripts/run_jmh.sh …
# scripts/run_jol_maps.sh
# scripts/run_kotlin_alloc.sh

LayoutCopy Anchor Link

docs/guide-src/     chapter sources (en/, zh-CN/)
docs/               assembled guides + corpus.md
examples/           java + kotlin (+ android fixtures)
jvmperf-lint/       Java checker (Gradle) + fixtures
jmh-benches/        JMH sources
lib/                optional jars (gitignored; fetch-lib.sh)
research/           small in-tree Jol/EA probe sources (no *.log dumps)
scripts/            run_*, check_*, env.sh (build_guide is superseded by the repo-level scripts/build-guides.sh)
evidence/           pointers to research JSONL (not full dumps)