by Andrew Brampton (bramp.net)
This is a collection of tools that make use of the sun.misc.Unsafe class. This Unsafe class allows direct access to memory within the JVM, which is extremely dangerous, but fun :).
- unsafe-helper - Contains some simple methods that make using sun.misc.Unsafe easier.
- unsafe-collection - An example List modelled on the ArrayList, which instead of storing reference to objects within
the collection, instead copies the elements directly into the list. This has a few interesting properties
- Less total memory is required for the list and contained objects. Reducing GC overheads.
- The objects are guranteed to be contingous in memory, which may provide some good CPU cache benefits.
- Objects are copied into the list, this copy overhead may not be worth it, and you lose many of the reference semantics you would be used t
- unsafe-unroller - At runtimes generates optomal bytecode to copy objects with the Unsafe class.
- unsafe-benchmark - Code to benchmark everything using the JMH framework.
- unsafe-tests - Some simple test classes to help with tests of the other modules.
Read about this in a series of articles:
- Part 1: sun.misc.Unsafe Helper Classes
- Part 2: Using sun.misc.Unsafe to create a contiguous array of objects
- Part 3: Benchmarking a java UnsafeArrayList
Requires Java 7 or higher. To include use the following Maven dependency:
<dependencies>
<dependency>
<groupId>net.bramp.unsafe</groupId>
<artifactId>unsafe-helper</artifactId>
<version>1.0</version>
</dependency>
</dependencies>To build use maven, e.g mvn
To release to maven central, we use the Sonatype OSS repo, and maven-release-plugin:
mvn release:prepare
mvn release:performRead more about the benchmarks at bramp.net
cd unsafe-benchmark
mvn
java -jar target/benchmarks.jar | tee logs
...
# JMH 1.10.3 (released 9 days ago)
# VM version: JDK 1.8.0_45-internal, VM 25.45-b02
Benchmark Mode Cnt Score Error Units
UnrolledCopierBenchmark.HandUnrolledState.test thrpt 25 438819259.527 ± 14364692.101 ops/s
UnrolledCopierBenchmark.LoopState.test thrpt 25 196408390.244 ± 2173851.339 ops/s
UnrolledCopierBenchmark.UnrolledState.test thrpt 25 458324068.892 ± 6192069.477 ops/s
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate ArrayList<LongPoint> 80000000 avgt 5 2.266 ± 0.229 s/op
ArrayListBenchmark.testIterate ArrayList<LongPoint> 20000000 avgt 5 0.552 ± 0.019 s/op
ArrayListBenchmark.testIterate ArrayList<LongPoint> 5000000 avgt 5 0.136 ± 0.004 s/op
ArrayListBenchmark.testSort ArrayList<LongPoint> 80000000 avgt 5 70.310 ± 3.939 s/op
ArrayListBenchmark.testSort ArrayList<LongPoint> 20000000 avgt 5 14.754 ± 0.541 s/op
ArrayListBenchmark.testSort ArrayList<LongPoint> 5000000 avgt 5 3.250 ± 0.139 s/op
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate UnsafeArrayList<LongPoint> 80000000 avgt 5 1.790 ± 0.030 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<LongPoint> 20000000 avgt 5 0.449 ± 0.016 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<LongPoint> 5000000 avgt 5 0.112 ± 0.001 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<LongPoint> 80000000 avgt 5 0.442 ± 0.023 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<LongPoint> 20000000 avgt 5 0.110 ± 0.003 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<LongPoint> 5000000 avgt 5 0.028 ± 0.002 s/op
ArrayListBenchmark.testSort UnsafeArrayList<LongPoint> 80000000 avgt 5 18.690 ± 3.158 s/op
ArrayListBenchmark.testSort UnsafeArrayList<LongPoint> 20000000 avgt 5 3.414 ± 0.034 s/op
ArrayListBenchmark.testSort UnsafeArrayList<LongPoint> 5000000 avgt 5 0.682 ± 0.014 s/op
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate ArrayList<FourLongs> 80000000 avgt 5 2.277 ± 0.211 s/op
ArrayListBenchmark.testIterate ArrayList<FourLongs> 20000000 avgt 5 0.557 ± 0.023 s/op
ArrayListBenchmark.testIterate ArrayList<FourLongs> 5000000 avgt 5 0.140 ± 0.007 s/op
ArrayListBenchmark.testSort ArrayList<FourLongs> 80000000 avgt 5 79.673 ± 6.119 s/op
ArrayListBenchmark.testSort ArrayList<FourLongs> 20000000 avgt 5 16.705 ± 1.353 s/op
ArrayListBenchmark.testSort ArrayList<FourLongs> 5000000 avgt 5 3.673 ± 0.156 s/op
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate UnsafeArrayList<FourLongs> 80000000 avgt 5 2.126 ± 0.019 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<FourLongs> 20000000 avgt 5 0.533 ± 0.004 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<FourLongs> 5000000 avgt 5 0.133 ± 0.002 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<FourLongs> 80000000 avgt 5 0.648 ± 0.019 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<FourLongs> 20000000 avgt 5 0.163 ± 0.005 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<FourLongs> 5000000 avgt 5 0.040 ± 0.006 s/op
ArrayListBenchmark.testSort UnsafeArrayList<FourLongs> 80000000 avgt 5 24.822 ± 0.790 s/op
ArrayListBenchmark.testSort UnsafeArrayList<FourLongs> 20000000 avgt 5 4.843 ± 0.075 s/op
ArrayListBenchmark.testSort UnsafeArrayList<FourLongs> 5000000 avgt 5 1.020 ± 0.017 s/op
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate ArrayList<EightLongs> 80000000 avgt 5 2.792 ± 0.072 s/op
ArrayListBenchmark.testIterate ArrayList<EightLongs> 20000000 avgt 5 0.564 ± 0.022 s/op
ArrayListBenchmark.testIterate ArrayList<EightLongs> 5000000 avgt 5 0.138 ± 0.007 s/op
ArrayListBenchmark.testSort ArrayList<EightLongs> 80000000 avgt 5 97.687 ± 4.860 s/op
ArrayListBenchmark.testSort ArrayList<EightLongs> 20000000 avgt 5 20.084 ± 1.124 s/op
ArrayListBenchmark.testSort ArrayList<EightLongs> 5000000 avgt 5 4.474 ± 0.248 s/op
Benchmark (clazz) (size) Mode Cnt Score Error Units
ArrayListBenchmark.testIterate UnsafeArrayList<EightLongs> 80000000 avgt 5 2.672 ± 0.322 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<EightLongs> 20000000 avgt 5 0.688 ± 0.014 s/op
ArrayListBenchmark.testIterate UnsafeArrayList<EightLongs> 5000000 avgt 5 0.171 ± 0.003 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<EightLongs> 80000000 avgt 5 0.941 ± 0.032 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<EightLongs> 20000000 avgt 5 0.236 ± 0.008 s/op
ArrayListBenchmark.testListIterateInPlace UnsafeArrayList<EightLongs> 5000000 avgt 5 0.058 ± 0.002 s/op
ArrayListBenchmark.testSort UnsafeArrayList<EightLongs> 80000000 avgt 5 40.697 ± 0.743 s/op
ArrayListBenchmark.testSort UnsafeArrayList<EightLongs> 20000000 avgt 5 7.608 ± 0.267 s/op
ArrayListBenchmark.testSort UnsafeArrayList<EightLongs> 5000000 avgt 5 1.729 ± 0.101 s/op