GsonBenchmark.java

package org.qwwdfsad.benchmarks;

import com.google.gson.Gson;
import org.openjdk.jmh.annotations.*;

import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Threads(8)
@Fork(value = 2)
@Warmup(iterations = 10)
@Measurement(iterations = 10)
@State(Scope.Thread)
public class GsonBenchmark {

    private static final Gson GSON = new Gson();
    private static final ThreadLocal<Gson> THREAD_LOCAL_GSON = new ThreadLocal<Gson>() {
        @Override
        protected Gson initialValue() {
            return new Gson();
        }
    };

    public static class Pojo {
        boolean bool;
        int i;
        long l;
        double d;
        String s;

      public Pojo(boolean bool, int i, long l, double d, String s) {
          this.bool = bool;
          this.i = i;
          this.l = l;
          this.d = d;
          this.s = s;
      }
    }

    // JMH allows using instance field as single state object
    private Pojo state = buildState();

    private Pojo buildState() {
        return new Pojo(true, 1, 2L, 3.0, "4");
    }

    @Benchmark
    public String deserializeThreadLocal() {
        return THREAD_LOCAL_GSON.get().toJson(state);
    }

    @Benchmark
    public String deserializeContended() {
        return GSON.toJson(state);
    }
}

results.txt

Original gson (2.6.3-SNAPSHOT)

Contended case:
java -jar target/benchmarks.jar -t -8 -gc true GsonBenchmark

Benchmark                              Mode  Cnt     Score     Error   Units
GsonBenchmark.deserializeContended    thrpt   20  1192.009 ± 49.979  ops/ms
GsonBenchmark.deserializeThreadLocal  thrpt   20  3645.967 ± 82.016  ops/ms

Sanity check: benchmark with only 1 thread should show ~same throughput for both plain and thread local Gson:

java -jar target/benchmarks.jar -t 1 -gc true GsonBenchmark

Benchmark                              Mode  Cnt     Score     Error   Units
GsonBenchmark.deserializeContended    thrpt   20  1011.861 ± 32.744  ops/ms
GsonBenchmark.deserializeThreadLocal  thrpt   20  1088.537 ± 31.451  ops/ms 


For patched Gson:
java -jar target/benchmarks.jar -t -8 -gc true GsonBenchmark
GsonBenchmark.deserializeContended    thrpt   20  4003.211 ± 164.599  ops/ms
GsonBenchmark.deserializeThreadLocal  thrpt   20  3997.017 ± 211.468  ops/ms

java -jar target/benchmarks.jar -t 1 -gc true GsonBenchmark
GsonBenchmark.deserializeContended    thrpt   20  1160.261 ± 25.967  ops/ms
GsonBenchmark.deserializeThreadLocal  thrpt   20  1131.689 ± 17.576  ops/ms