ci(performance): add daily JMH benchmark workflow

Switch exec-maven-plugin from exec:java to exec:exec to pass explicit
JVM flags. Always write JMH results to target/benchmark-result.json.
Add github-action-benchmark workflow (20:00 UTC = 22:00 CEST) that
stores history on gh-pages and alerts on >30% regression.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

.github/workflows/benchmark.yml

@@ -0,0 +1,57 @@
+name: Benchmarks
+
+on:
+  schedule:
+    - cron: '0 20 * * *'  # 22:00 CEST / 21:00 CET
+  workflow_dispatch:
+
+jobs:
+  benchmark:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Azul Zulu JDK 25
+        uses: actions/setup-java@v4
+        with:
+          distribution: zulu
+          java-version: '25'
+
+      - name: Cache Maven repository
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
+
+      - name: Install protobuf compiler
+        run: sudo apt-get install -y protobuf-compiler
+
+      - name: Install flatc 25.12.19
+        run: |
+          curl -fsSL -o flatc.zip https://github.com/google/flatbuffers/releases/download/v25.12.19/Linux.flatc.binary.g++-13.zip
+          unzip -j flatc.zip flatc
+          sudo install -m 755 flatc /usr/local/bin/flatc
+
+      - name: Build
+        run: ./mvnw compile -pl performance -am -DskipTests -q
+
+      - name: Run benchmarks
+        run: ./mvnw exec:exec -pl performance -DskipTests
+
+      - name: Store benchmark results
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          tool: jmh
+          output-file-path: performance/target/benchmark-result.json
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          auto-push: true
+          alert-threshold: '130%'
+          comment-on-alert: true
+          fail-on-alert: false
+          gh-pages-branch: gh-pages
+          benchmark-data-dir-path: dev/bench

CLAUDE.md

@@ -47,13 +47,13 @@ Never use `mvn install` or `./mvwn install`.
 ./mvnw verify -pl integration -am -Dit.test="RustWritesJavaReadsIntegrationTest#s3_pcoVortex_javaDecodeMatchesJni"
 
 # Run all benchmarks
-./mvnw compile exec:java -pl performance -am -DskipTests
+./mvnw compile -pl performance -am -DskipTests -q && ./mvnw exec:exec -pl performance -DskipTests
 
 # Run specific benchmark class
-./mvnw compile exec:java -pl performance -am -DskipTests -Dexec.args="RustVsJavaReadBenchmark"
+./mvnw compile -pl performance -am -DskipTests -q && ./mvnw exec:exec -pl performance -DskipTests -Dbenchmark=RustVsJavaReadBenchmark
 
 # Run specific benchmark method (always use ClassName.methodName filter)
-./mvnw compile exec:java -pl performance -am -DskipTests -Dexec.args="RustVsJavaReadBenchmark.javaReadVolume"
+./mvnw compile -pl performance -am -DskipTests -q && ./mvnw exec:exec -pl performance -DskipTests -Dbenchmark=RustVsJavaReadBenchmark.javaReadVolume
 ```
 
 ### File format

performance/pom.xml

@@ -11,6 +11,13 @@
 
 	<artifactId>performance</artifactId>
 
+	<properties>
+		<!-- Override with -Dbenchmark="ClassName.methodName" to run a specific benchmark -->
+		<benchmark>.*</benchmark>
+		<!-- JMH output: override with -Djmh.outputFile=/dev/null to suppress -->
+		<jmh.outputFile>${project.build.directory}/benchmark-result.json</jmh.outputFile>
+	</properties>
+
 	<dependencies>
 		<dependency>
 			<groupId>io.github.dfa1.vortex</groupId>
@@ -74,12 +81,26 @@
 					</annotationProcessorPaths>
 				</configuration>
 			</plugin>
-			<!-- Run benchmarks: ./mvnw compile exec:java -pl performance -am -DskipTests -Dexec.args="ClassName.method" -->
+			<!-- Run benchmarks: ./mvnw compile -pl performance -am -DskipTests -q && ./mvnw exec:exec -pl performance -DskipTests [-Dexec.args="ClassName.methodName"] -->
 			<plugin>
 				<groupId>org.codehaus.mojo</groupId>
 				<artifactId>exec-maven-plugin</artifactId>
 				<configuration>
-					<mainClass>org.openjdk.jmh.Main</mainClass>
+					<executable>java</executable>
+					<arguments>
+						<argument>--add-opens</argument>
+						<argument>java.base/java.nio=ALL-UNNAMED</argument>
+						<argument>--enable-native-access=ALL-UNNAMED</argument>
+						<argument>--sun-misc-unsafe-memory-access=allow</argument>
+						<argument>-classpath</argument>
+						<classpath/>
+						<argument>org.openjdk.jmh.Main</argument>
+					<argument>${benchmark}</argument>
+					<argument>-rf</argument>
+					<argument>json</argument>
+					<argument>-rff</argument>
+					<argument>${jmh.outputFile}</argument>
+					</arguments>
 				</configuration>
 			</plugin>
 		</plugins>