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Alan Paxton f8969ad7d4 Improve Java API get() performance by reducing copies (#10970) 
Summary:
Performance improvements for `get()` paths in the RocksJava API (JNI).
Document describing the performance results.

Replace uses of the legacy `DB::Get()` method wrapper returning data in a `std::string` with direct calls to `DB::Get()` passing a pinnable slice to receive this data. Copying from a pinned slice direct to the destination java byte array, without going via an intervening std::string, is a major performance gain for this code path.

Note that this gain only comes where `DB::Get()` is able to return a pinned buffer; where it has to copy into the buffer owned by the slice, there is still the intervening copy and no performance gain. It may be possible to address this case too, but it is not trivial.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10970

Reviewed By: pdillinger

Differential Revision: D42125567

Pulled By: ajkr

fbshipit-source-id: b7a4df7523b0420cadb1e9b6c7da3ec030a8da34
 		2022-12-21 11:54:24 -08:00
..
src/main/java/org/rocksdb Improve Java API get() performance by reducing copies (#10970) 2022-12-21 11:54:24 -08:00
LICENSE-HEADER.txt JMH microbenchmarks for RocksJava (#6241) 2020-01-07 15:46:09 -08:00
README.md java / jni io_uring support (#9224) 2021-12-15 18:09:25 -08:00
pom.xml Improve Java API get() performance by reducing copies (#10970) 2022-12-21 11:54:24 -08:00

README.md

JMH Benchmarks for RocksJava

These are micro-benchmarks for RocksJava functionality, using JMH (Java Microbenchmark Harness).

Compiling

Note: This uses a specific build of RocksDB that is set in the <version> element of the dependencies section of the pom.xml file. If you are testing local changes you should build and install a SNAPSHOT version of rocksdbjni, and update the pom.xml of rocksdbjni-jmh file to test with this.

For instance, this is how to install the OSX jar you just built for 6.26.0

$ mvn install:install-file -Dfile=./java/target/rocksdbjni-6.26.0-SNAPSHOT-osx.jar -DgroupId=org.rocksdb -DartifactId=rocksdbjni -Dversion=6.26.0-SNAPSHOT -Dpackaging=jar

$ mvn package

Running

$ java -jar target/rocksdbjni-jmh-1.0-SNAPSHOT-benchmarks.jar

NOTE: you can append -help to the command above to see all of the JMH runtime options.