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Performance comparison

In the following article we'd like to present some performance comparions of our Java compilation task compared to other existing solutions.

All the comparisons are done on the same and single machine. The comparions are done on Windows 10, with the Windows Defender being turned off all times. When doing the comparisons, we'll be using the build daemons of each participating tool when applicable.

During the measurements, we'll be doing some warm-up round(s) for each tools which won't be part of the result. Then we compute the average of the measured times and that will be the result of a measurement. We don't use any benchmarking/profiling tools, and don't set any options that instrument the tools for benchmarking.

We'll use the Measure-Command PowerShell cmdlet to measure the time it takes to execute a build. (We use the time the cmdlet displays instead that the given tool displays to have a consistent measuring practice.) Note that when the tools are used inside an IDE, the startup cost of the Java processes may be omitted.

When clean builds are measured, the previous outputs are manually cleaned from the output directory rather than running clean commands for a given tool.

The following comparisons will focus plainly on clean and incremental Java compilation. If you're interested in Java testing performance comparison, have a look here.

Gradle comparison

In the following measurements we'll be focusing on the Gradle build tool. It is popular in the JVM ecosystem, and also supports other languages. We won't be directly comparing to Maven, as one can deduce the results based on our and the Gradle vs Maven performance comparison.

In our tests we'll be performing the same test-case scenarios that the Gradle team used vs Maven. We'll also add some other comparisons that include annotation processing and other use-cases.

We'll be using the (currently latest) 6.0.1 version of Gradle in the following tests.

Apache Commons Lang

For this measurement we take the current latest available version of the master branch, and perform clean and incremental compilations.

Apache Commons Lang
Test caseSaker.buildGradle 6.0.1
Clean build22272698
No-op (no changes)5791307
Incremental NumberUtils.java7931641
Incremental DiffResult.java7312693

We can see that is faster in all cases. It performs the clean build 17.5% faster, while the advantage for incremental compilations grows over 50-70%.

The test case includes two incremental compilation scenarios. In both of them we just simple insert a new line at the start of the file to force its recompilation. The significant difference between them that the DiffResult class contains a constant field. In these cases Gradle falls back to full recompilation of the entire Java source set. As we are very fond of constants, we felt that a comparison for this needed to be included.

Large multi-project

In the following measurement we compile a project that contains of multiple cross-dependent Java subprojects. We took the Gradle large multi-project codebase as the basis of the test, removed unnecesssary testing and library classpath code, and simplified the Gradle build process to have a fair comparison.

We also used the --parallel flag when invoking Gradle, as without it the builds were much slower. The actual project that was built is available here.

Large multi-project build
Test caseSaker.buildGradle 6.0.1
Clean build2013336774
No-op (no changes)10403260
Incremental ABI keeping11903541
Incremental ABI changing40626979 produced 40-70% faster build times for the above scenarios. When measuring the incremental builds, we separated them into two category. One which doesn't modify the structure of the Java classes (Application Binary Interface keeping), and one that changes the class structure (ABI changing). In both cases the project1/src/main/java/org/gradle/test/performance1_4/ file was modified.

When the ABI is kept, we just added a new line at the start of the file to cause the recompilation of the source file. In this case only the modified source file was recompiled, and no other dependent subprojects are compiled again. This is true for both and Gradle.

For the ABI changing tests, we added a new public int i field for every measurement that we've performed. This causes all the subprojects which depend on the structure of the Production1_315 class to be recompiled. In the end, multiple subprojects are recompiled. This was the case where the difference between the two tools were the smallest, is only 41% faster than Gradle.

Large monolithic project

Next up is a measurement that compiles large amount of Java sources in a single compilation pass. The project is taken from the Gradle single-large-project performance comparion scenario, and we measured both tools by running the builds. We've cleaned up the Gradle build file so it doesn't include unnecessary dependencies and IDE plugins.

Large monolithic build
Test caseSaker.buildGradle 6.0.1
Clean build3125862419
No-op (no changes)6113329
Incremental ABI keeping12875879
Incremental ABI changing13605897

Although the graph is a bit out of scale due to the huge differences between the clean and incremental build times, we can still see that is 50-80% faster in all of the above test cases. The ABI keeping and ABI changing scenarios were done similarly to the Large multi-project scenario.

Annotation processing

We'd like to include tests for incremental scenarios using annotation processors, however, we encountered such bugs in the Gradle build system that prevented running them. We wanted to test two annotation processors (one aggregating, one isolating), however, the Gradle builds resulted in compilation errors and stackoverflows.

We'll be running the measurements once the issue 11559 is fixed by Gradle.


Based on the above measurements we can see that task of the system can perform Java builds significantly faster. If we decide to use inside an IDE, then the incremental compilation times can shrink even more, as the startup time of the JVM can be omitted. This usually results in a decrease of 500-600 ms for the build times.

If the results convinced you, and you feel like may be an appropriate tool for you use-case, we recommend trying it out.