Core Java

How much faster is Java 8?

Java SE 8 was released yesterday. Traditionally, every new major JRE version comes with a free performance boost. Do we get another free lunch? And how big is the gain this time?

Let’s benchmark it.

Benchmark methodology

  • Run the same code with 3 different JRE versions (SunJDK 1.6.0_26, OpenJDK 1.7.0_51 and OpenJDK 1.8.0). The code itself was written for Java 6 (both in syntax and JDK API’s usage) and compiled for Java 6 with OpenJDK 1.7.
  • Each run takes about 55 minutes.
  • VM arguments: -Xmx1536M -server
    Software: Linux 3.2.0-59-generic-pae
    Hardware: Intel® Xeon® CPU W3550 @ 3.07GHz
  • Each run solves 13 planning problems with OptaPlanner. Each planning problem runs for 5 to minutes. Up to 2 planning problems are solved in parallel.
  • Solving a planning problem involves no IO (except a few milliseconds during startup to load the input). A single CPU is completely saturated. It constantly creates many short lived objects, and the GC collects them afterwards.
  • The benchmarks measure the number of scores that can be calculated per millisecond. Higher is better. Calculating a score for a proposed planning solution is non-trivial: it involves many calculations, including checking for conflicts between every entity and every other entity.

To reproduce this benchmark locally, build optaplanner from source and run the main class GeneralOptaPlannerBenchmarkApp.

Benchmark results

Executive summary


My observations:

  • On the biggest dataset (Machine Reassignment B10), which dwarfs any of the other datasets in size, Java 8 is 20% faster than Java 7, which was already 17% faster than Java 6.
  • In some cases, Java 8 is slower than Java 7. Specially for the course scheduling datasets, Java 8 is 6% slower than Java 7. Hopefully new releases of Java 8 will resolve this performance regression soon.
  • On average, Java 8 is only 1% faster than Java 7. This while Java 7 is already 16% faster than Java 6.
  • Despite that this is the first final release of OpenJDK 8, I did not find any regressions in Java 8. OptaPlanner’s examples are 100% reproducible, so as expected, the different JRE’s give the exact same results at every single iteration.

Raw benchmark numbers

JDKCloud balancing 200cCloud balancing 800cMachine reassignment B1Machine reassignment B10Course scheduling c7Course scheduling c8Exam scheduling s2Exam scheduling s3Nurse rostering m1Nurse rostering mh1Sport scheduling nl14
SunJDK 1.6.0_26464624496394567286555473698969543785323229481977
OpenJDK 1.7.0_515368349798116553337336182784882434606364533772445
OpenJDK 1.8.05468751625135102405295798735780484441363733242321
6 ⇒ 715.54%10.75%23.25%17.72%12.95%12.29%18.54%21.69%12.78%14.55%23.67%
7 ⇒ 81.87%3.67%15.91%20.15%-6.21%-6.26%-2.37%-3.58%-0.22%-1.57%-5.07%
Dataset scale120k1920k500k250000k217k145k1705k1613k18k12k4k


On the big datasets, Java 8 is clearly faster. And this without changing a line of code. On average, the result is less convincing (with the current release), but a free lunch is always welcome.

Reference: How much faster is Java 8? from our JCG partner Geoffrey De Smet at the OptaPlanner blog.

Geoffrey De Smet

Geoffrey De Smet (Red Hat) is the lead and founder of OptaPlanner. Before joining Red Hat in 2010, he was formerly employed as a Java consultant, an A.I. researcher and an enterprise application project lead. He has contributed to many open source projects (such as drools, jbpm, pressgang, spring-richclient, several maven plugins, weld, arquillian, ...). Since he started OptaPlanner in 2006, he’s been passionately addicted to planning optimization.
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9 years ago

Seriously? openjdk? seriously? java 8? openjdk? seriously man?

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