1.x: benchmark just() and its optimizations.

src/perf/java/rx/ScalarJustPerf.java

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+/**
+ * Copyright 2014 Netflix, Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package rx;
+
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.infra.Blackhole;
+
+import rx.functions.Func1;
+import rx.jmh.LatchedObserver;
+import rx.schedulers.Schedulers;
+
+/**
+ * Benchmark the cost of just and its various optimizations.
+ * <p>
+ * gradlew benchmarks "-Pjmh=-f 1 -tu s -bm thrpt -wi 5 -i 5 -r 1 .*ScalarJustPerf.*"
+ * <p>
+ * gradlew benchmarks "-Pjmh=-f 1 -tu ns -bm avgt -wi 5 -i 5 -r 1 .*ScalarJustPerf.*"
+ */
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+@State(Scope.Thread)
+public class ScalarJustPerf {
+    /** A subscriber without a CountDownLatch; use it for synchronous testing only. */
+    static final class PlainSubscriber extends Subscriber<Integer> {
+        final Blackhole bh;
+        public PlainSubscriber(Blackhole bh) {
+            this.bh = bh;
+        }
+
+        @Override
+        public void onNext(Integer t) {
+            bh.consume(t);
+        }
+
+        @Override
+        public void onError(Throwable e) {
+            bh.consume(e);
+        }
+
+        @Override
+        public void onCompleted() {
+            bh.consume(false);
+        }
+    }
+
+    /** This is a simple just. */
+    Observable<Integer> simple;
+    /** 
+     * This is a simple just observed on the computation scheduler.
+     * The current computation scheduler supports direct scheduling and should have
+     * lower overhead than a regular createWorker-use-unsubscribe.
+     */
+    Observable<Integer> observeOn;
+    /** This is a simple just observed on the IO thread. */
+    Observable<Integer> observeOnIO;
+
+    /** 
+     * This is a simple just subscribed to on the computation scheduler.
+     * In theory, for non-backpressured just(), this should be the
+     * same as observeOn.
+     */
+    Observable<Integer> subscribeOn;
+    /** This is a simple just subscribed to on the IO scheduler. */
+    Observable<Integer> subscribeOnIO;
+
+    /** This is a just mapped to itself which should skip the operator flatMap completely. */
+    Observable<Integer> justFlatMapJust;
+    /** 
+     * This is a just mapped to a range of 2 elements; it tests the case where the inner
+     * Observable isn't a just().
+     */
+    Observable<Integer> justFlatMapRange;
+
+    @Setup
+    public void setup() {
+        simple = Observable.just(1);
+
+        observeOn = simple.observeOn(Schedulers.computation());
+        observeOnIO = simple.observeOn(Schedulers.io());
+
+        subscribeOn = simple.subscribeOn(Schedulers.computation());
+        subscribeOnIO = simple.subscribeOn(Schedulers.io());
+
+        justFlatMapJust = simple.flatMap(new Func1<Integer, Observable<Integer>>() {
+            @Override
+            public Observable<Integer> call(Integer v) {
+                return Observable.just(v);
+            }
+        });
+
+        justFlatMapRange = simple.flatMap(new Func1<Integer, Observable<Integer>>() {
+            @Override
+            public Observable<Integer> call(Integer v) {
+                return Observable.range(v, 2);
+            }
+        });
+    }
+
+    /**
+     * Common routine to create a latched observer, subscribe it to the
+     * given source and spin-wait for its completion.
+     * <p>Don't use this with long sources. The spin-wait is there
+     * to avoid operating-system level scheduling-wakeup granularity problems with
+     * short sources.
+     * @param bh the black hole to sink values and prevent dead code elimination
+     * @param source the source observable to observe
+     */
+    void runAsync(Blackhole bh, Observable<Integer> source) {
+        LatchedObserver<Integer> lo = new LatchedObserver<Integer>(bh);
+
+        source.subscribe(lo);
+
+        while (lo.latch.getCount() != 0L);
+    }
+
+    @Benchmark
+    public void simple(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        simple.subscribe(s);
+    }
+
+    @Benchmark
+    public void simpleEscape(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        bh.consume(s);
+        simple.subscribe(s);
+    }
+
+    @Benchmark
+    public Object simpleEscapeAll(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        bh.consume(s);
+        return simple.subscribe(s);
+    }
+
+    @Benchmark
+    public void observeOn(Blackhole bh) {
+        runAsync(bh, observeOn);
+    }
+
+    @Benchmark
+    public void observeOnIO(Blackhole bh) {
+        runAsync(bh, observeOnIO);
+    }
+
+    @Benchmark
+    public void subscribeOn(Blackhole bh) {
+        runAsync(bh, subscribeOn);
+    }
+
+    @Benchmark
+    public void subscribeOnIO(Blackhole bh) {
+        runAsync(bh, subscribeOnIO);
+    }
+
+    @Benchmark
+    public void justFlatMapJust(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        justFlatMapJust.subscribe(s);
+    }
+
+    @Benchmark
+    public void justFlatMapJustEscape(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        bh.consume(s);
+        justFlatMapJust.subscribe(s);
+    }
+
+    @Benchmark
+    public void justFlatMapRange(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        justFlatMapRange.subscribe(s);
+    }
+
+    @Benchmark
+    public void justFlatMapRangeEscape(Blackhole bh) {
+        PlainSubscriber s = new PlainSubscriber(bh);
+        bh.consume(s);
+        justFlatMapRange.subscribe(s);
+    }
+}