java-perf-tests

JMH microbenchmark project for comparing JVM performance across implementations and JDK versions.

Requirements

• Maven 3.x
• JDK 17 (used to build)
• JDK 17 / 21 / 25 for running benchmarks (configure paths in set-env.sh)

Setup

Copy the environment template and set your local JDK paths:

cp set-env.sh.template set-env.sh
# edit set-env.sh to point JDK_HOME_17/21/25 to your installations

Building

mvn clean package

Produces target/benchmarks.jar.

Running benchmarks

./run-benchmarks.sh [options] [benchmark-filter] [JMH args...]

Options:
  -p <name=value>   Pass a JMH @Param value (repeatable)
  -j <version>      JDK version: 17, 21, 25, or all (default: 21)
  -prof <profiler>  JMH profiler (e.g. xctraceasm, async, gc)
  -h                Show help

Examples:

# Run all benchmarks on JDK 21
./run-benchmarks.sh

# Run on all JDK versions
./run-benchmarks.sh -j all

# Filter by benchmark class
./run-benchmarks.sh AsciiCheckerBenchmark
./run-benchmarks.sh UTF8ValidatorBenchmark

# Filter by param values
./run-benchmarks.sh -p impl=swar -p 'stringType=long ASCII' AsciiCheckerBenchmark

# Run with a profiler
./run-benchmarks.sh -prof xctraceasm -p impl=swar AsciiCheckerBenchmark

# Run across all JDKs with a specific string type
./run-benchmarks.sh -j all -p 'stringType=long ASCII'

Each run saves output to logs/<benchmark>-YYYYMMDD-HHMMSS.log. If compiler assembly output is present, it is extracted into a separate logs/<benchmark>-YYYYMMDD-HHMMSS-compiler.log.

Benchmarks

ASCII checking (org.github.netudima.perf.tests.ascii)

Checks whether a byte array contains only ASCII characters.

impl	Description
simple	Scalar loop with index (bytes[i] < 0)
simple-foreach	Scalar loop with foreach (for (byte b : bytes))
swar	SWAR: 8 bytes at a time via VarHandle + 0x8080808080808080 mask

Params: impl, stringType

UTF-8 validation (org.github.netudima.perf.tests.utf8)

Validates whether a byte array is well-formed UTF-8. Logic derived from Apache Cassandra's UTF8Serializer, adapted to work directly on byte[].

impl	Description
simple	Scalar ASCII fast path + full UTF-8 state-machine slow path
swar	SWAR 8-bytes-at-a-time ASCII fast path + same slow path

Params: impl, stringType

String types

Both benchmarks use the same five stringType values:

Value	Description
short ASCII	Short all-ASCII string
long ASCII	Long all-ASCII string (~450 bytes)
short ASCII prefix non-ASCII	Short string with ASCII prefix followed by non-ASCII
short non-ASCII	Short string starting with non-ASCII immediately
long non-ASCII	Long Braille Unicode string