# HG changeset patch # User martin # Date 1556726772 25200 # Wed May 01 09:06:12 2019 -0700 # Node ID 1b5f0a3f9c4175f0f6ab05efc93cf367d8e0cf10 # Parent f14a826e3c2e49f79266dc7324697e61d196944d 8223078: Add microbenchmark for array copying/clearing/resizing Reviewed-by: dl, redestad diff --git a/test/micro/org/openjdk/bench/java/lang/ArrayFiddle.java b/test/micro/org/openjdk/bench/java/lang/ArrayFiddle.java new file mode 100644 --- /dev/null +++ b/test/micro/org/openjdk/bench/java/lang/ArrayFiddle.java @@ -0,0 +1,195 @@ +/* + * Copyright 2019 Google Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ +package org.openjdk.bench.java.lang; + +import org.openjdk.jmh.annotations.Benchmark; +import org.openjdk.jmh.annotations.BenchmarkMode; +import org.openjdk.jmh.annotations.Mode; +import org.openjdk.jmh.annotations.OutputTimeUnit; +import org.openjdk.jmh.annotations.Param; +import org.openjdk.jmh.annotations.Scope; +import org.openjdk.jmh.annotations.Setup; +import org.openjdk.jmh.annotations.State; + +import java.util.Arrays; +import java.util.concurrent.ThreadLocalRandom; +import java.util.concurrent.TimeUnit; + +/** + * Explores the cost of copying the contents of one array to another, as is + * commonly seen in collection classes that need to resize their backing + * array, like ArrayList. + * + * We have multiple variations on copying, and we explore the cost of + * clearing the old array, which might help for generational GCs. + * + * Benchmarks the operations in the ancient + * JDK-6428387: array clone() much slower than Arrays.copyOf + * + * 2019 results on x86: + * + * The "simple" benchmarks below have the same performance, except that + * simple_copyLoop is surprisingly 5x slower. The array copying intrinsics + * are very effective and a naive loop does not get optimized the same way. + * OTOH there is no intrinsic for Arrays.fill but the naive array zeroing loop + * *does* get optimized to something a little faster than than arraycopy. + * + * System.arraycopy and Arrays.fill have such outstanding performance that + * one should use them to replace handwritten loops whenever possible. + * + * This benchmark is great for measuring cache effects, e.g. size=10^6 has 5x + * the per-element cost of size=10^3 (See "The Myth of RAM".) + * + * (cd $(hg root) && for size in 3 16 999 999999; do make test TEST="micro:java.lang.ArrayFiddle" MICRO="FORK=2;WARMUP_ITER=4;ITER=4;OPTIONS=-opi $size -p size=$size" |& perl -ne 'print if /^Benchmark/ .. /^Finished running test/'; done) + */ +@BenchmarkMode(Mode.AverageTime) +@OutputTimeUnit(TimeUnit.NANOSECONDS) +@State(Scope.Benchmark) +public class ArrayFiddle { + @Param("999") + public int size; + + public int largerSize; + public Object[] data; + public Object[] copy; + + @Setup + public void setup() { + largerSize = size + (size >> 1); + + data = new Object[size]; + ThreadLocalRandom rnd = ThreadLocalRandom.current(); + for (int i = data.length; i--> 0; ) + data[i] = rnd.nextInt(256); + + copy = data.clone(); + } + + // --- "simple" benchmarks just make an array clone + + @Benchmark + public Object[] simple_clone() { + return data.clone(); + } + + @Benchmark + public Object[] simple_copyOf() { + return Arrays.copyOf(data, data.length); + } + + @Benchmark + public Object[] simple_arraycopy() { + Object[] out = new Object[data.length]; + System.arraycopy(data, 0, out, 0, data.length); + return out; + } + + @Benchmark + public Object[] simple_copyLoop() { + final Object[] data = this.data; + int len = data.length; + Object[] out = new Object[len]; + for (int i = 0; i < len; i++) + out[i] = data[i]; + return out; + } + + // --- "grow" benchmarks have an output array that is larger + + private Object[] input_array() { + System.arraycopy(data, 0, copy, 0, size); + return copy; + } + + @Benchmark + public Object[] grow_copyLoop() { + Object[] in = input_array(); + Object[] out = new Object[largerSize]; + for (int i = 0, len = in.length; i < len; i++) + out[i] = in[i]; + return out; + } + + @Benchmark + public Object[] grow_copyZeroLoop() { + Object[] in = input_array(); + Object[] out = new Object[largerSize]; + for (int i = 0, len = in.length; i < len; i++) { + out[i] = in[i]; + in[i] = null; + } + return out; + } + + @Benchmark + public Object[] grow_arraycopy() { + Object[] in = input_array(); + Object[] out = new Object[largerSize]; + System.arraycopy(in, 0, out, 0, size); + return out; + } + + @Benchmark + public Object[] grow_arraycopy_fill() { + Object[] in = input_array(); + Object[] out = new Object[largerSize]; + System.arraycopy(in, 0, out, 0, size); + Arrays.fill(in, null); + return out; + } + + @Benchmark + public Object[] grow_arraycopy_zeroLoop() { + Object[] in = input_array(); + Object[] out = new Object[largerSize]; + System.arraycopy(in, 0, out, 0, size); + for (int i = 0, len = in.length; i < len; i++) + in[i] = null; + return out; + } + + @Benchmark + public Object[] grow_copyOf() { + Object[] in = input_array(); + Object[] out = Arrays.copyOf(in, largerSize); + return out; + } + + @Benchmark + public Object[] grow_copyOf_fill() { + Object[] in = input_array(); + Object[] out = Arrays.copyOf(in, largerSize); + Arrays.fill(in, null); + return out; + } + + @Benchmark + public Object[] grow_copyOf_zeroLoop() { + Object[] in = input_array(); + Object[] out = Arrays.copyOf(in, largerSize); + for (int i = 0, len = in.length; i < len; i++) + in[i] = null; + return out; + } + +}