Java 数组.stream（）.map（）.sum（）的性能不稳定
我偶然发现了一个非常不稳定的实例，它在基本数组上执行非常简单的map/reduce操作。以下是我的jmh基准代码：Java 数组.stream（）.map（）.sum（）的性能不稳定,java,java-8,jmh,Java,Java 8,Jmh,我偶然发现了一个非常不稳定的实例，它在基本数组上执行非常简单的map/reduce操作。以下是我的jmh基准代码： @OutputTimeUnit(TimeUnit.NANOSECONDS) @BenchmarkMode(Mode.AverageTime) @OperationsPerInvocation(Measure.ARRAY_SIZE) @Warmup(iterations = 300, time = 200, timeUnit=MILLISECONDS) @Measurement(it
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@BenchmarkMode(Mode.AverageTime)
@OperationsPerInvocation(Measure.ARRAY_SIZE)
@Warmup(iterations = 300, time = 200, timeUnit=MILLISECONDS)
@Measurement(iterations = 1, time = 1000, timeUnit=MILLISECONDS)
@State(Scope.Thread)
@Threads(1)
@Fork(1)
public class Measure
{
static final int ARRAY_SIZE = 1<<20;
final int[] ds = new int[ARRAY_SIZE];
private IntUnaryOperator mapper;
@Setup public void setup() {
setAll(ds, i->(int)(Math.random()*(1<<7)));
final int multiplier = (int)(Math.random()*10);
mapper = d -> multiplier*d;
}
@Benchmark public double multiply() {
return Arrays.stream(ds).map(mapper).sum();
}
}
JIT将首先编译在数组元素上迭代和操作（map/reduce）的热循环。这种情况很早就发生了，因为数组包含220个元素 稍后，JIT编译管道，很可能是在已编译的基准方法中内联的，由于内联限制，无法将其全部编译成一个方法。恰好在热循环中达到了这些内联限制，对map或sum的调用没有内联，所以热循环无意中被“去优化” 运行基准测试时，使用选项
-XX:+UnlockDiagnosticVMOptions-XX:+PrintCompilation-XX:+PrintInLine 1202 487 % 4 java.util.Spliterators$IntArraySpliterator::forEachRemaining @ 49 (68 bytes)
@ 53 java.util.stream.IntPipeline$3$1::accept (23 bytes) inline (hot)
\-> TypeProfile (1186714/1186714 counts) = java/util/stream/IntPipeline$3$1
@ 12 test.Measure$$Lambda$2/1745776415::applyAsInt (9 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = test/Measure$$Lambda$2
@ 5 test.Measure::lambda$setup$1 (4 bytes) inline (hot)
@ 17 java.util.stream.ReduceOps$5ReducingSink::accept (19 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 10 java.util.stream.IntPipeline$$Lambda$3/1779653790::applyAsInt (6 bytes) inline (hot)
\-> TypeProfile (1048064/1048064 counts) = java/util/stream/IntPipeline$$Lambda$3
@ 2 java.lang.Integer::sum (4 bytes) inline (hot)
%@16 java.util.stream.IntPipeline:：sum（11字节）内联（热）
\->TypeProfile（5120/5120计数）=java/util/stream/IntPipeline$3
@2 java.lang.invoke.LambdaForm$MH/12799022262:：linkToTargetMethod（8字节）强制按注释内联
@4 java.lang.invoke.LambdaForm$MH/1847865997:：identity（18字节）强制按注释内联
@14 java.lang.invoke.LambdaForm$DMH/2024969684:：invokeStatic_L_L（14字节）强制按注释内联
@1 java.lang.invoke.DirectMethodHandle:：internalMemberName（8字节）强制按注释内联
@10 sun.invoke.util.ValueConversions:：identity（2字节）内联（热）
@7 java.util.stream.IntPipeline:：reduce（16字节）内联（热）
@3 java.util.stream.ReduceOps:：makeInt（18字节）内联（热）
@1 java.util.Objects:：requireNonNull（14字节）内联（热）
@14 java.util.stream.ReduceOps$5:：（16字节）内联（热）
@12 java.util.stream.ReduceOps$ReduceOp:：（10字节）内联（热）
@1 java.lang.Object:：（1字节）内联（热）
@6 java.util.stream.AbstractPipeline:：evaluate（94字节）内联（热）
@50 java.util.stream.AbstractPipeline:：isParallel（8字节）内联（热）
@80 java.util.stream.TerminalOp:：getOpFlags（2字节）内联（热）
\->TypeProfile（5122/5122计数）=java/util/stream/ReduceOps$5
@85 java.util.stream.AbstractPipeline:：sourceSpliterator（163字节）内联（热）
@79 java.util.stream.AbstractPipeline:：isParallel（8字节）内联（热）
@88 java.util.stream.ReduceOps$ReduceOp:：evaluateSequential（18字节）内联（热）
@2 java.util.stream.ReduceOps$5:：makeSink（5字节）内联（热）
@1 java.util.stream.ReduceOps$5:：makeSink（16字节）内联（热）
@12 java.util.stream.ReduceOps$5ReduceInLink:：（15字节）内联（热）
@11 java.lang.Object:：（1字节）内联（热）
@6 java.util.stream.AbstractPipeline:：wrapAndCopyInto（18字节）内联（热）
@3 java.util.Objects:：requireNonNull（14字节）内联（热）
@9 java.util.stream.AbstractPipeline:：wrapSink（37字节）内联（热）
@1 java.util.Objects:：requireNonNull（14字节）内联（热）
@23 java.util.stream.IntPipeline$3:：opWrapSink（10字节）内联（热）
\->TypeProfile（4868/4868计数）=java/util/stream/IntPipeline$3
@6 java.util.stream.IntPipeline$3$1:（11字节）内联（热）
@7 java.util.stream.Sink$ChainedInt:：（16字节）内联（热）
@1 java.lang.Object:：（1字节）内联（热）
@6 java.util.Objects:：requireNonNull（14字节）内联（热）
@13 java.util.stream.AbstractPipeline:：copyInto（53字节）内联（热）
@1 java.util.Objects:：requireNonNull（14字节）内联（热）
@9 java.util.stream.AbstractPipeline:：getStreamAndOpFlags（5字节）访问器
@12 java.util.stream.StreamOpFlag:：isKnown（19字节）内联（热）
@20 java.util.Spliterator:：getExactSizeIfKnown（25字节）内联（热）
\->TypeProfile（4870/4870计数）=java/util/Spliterators$IntArraySpliterator
@1 java.util.Spliterators$IntArraySpliterator:：characteristics（5字节）访问器
@19 java.util.Spliterators$IntArraySpliterator:：estimateSize（11字节）内联（热）
@25 java.util.stream.Sink$chainedit:：begin（11字节）内联（热）
\->类型配置文件（4870/4870计数）=
$ java -version
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)
1202 487 % 4 java.util.Spliterators$IntArraySpliterator::forEachRemaining @ 49 (68 bytes)
@ 53 java.util.stream.IntPipeline$3$1::accept (23 bytes) inline (hot)
\-> TypeProfile (1186714/1186714 counts) = java/util/stream/IntPipeline$3$1
@ 12 test.Measure$$Lambda$2/1745776415::applyAsInt (9 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = test/Measure$$Lambda$2
@ 5 test.Measure::lambda$setup$1 (4 bytes) inline (hot)
@ 17 java.util.stream.ReduceOps$5ReducingSink::accept (19 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 10 java.util.stream.IntPipeline$$Lambda$3/1779653790::applyAsInt (6 bytes) inline (hot)
\-> TypeProfile (1048064/1048064 counts) = java/util/stream/IntPipeline$$Lambda$3
@ 2 java.lang.Integer::sum (4 bytes) inline (hot)
@ 16 java.util.stream.IntPipeline::sum (11 bytes) inline (hot)
\-> TypeProfile (5120/5120 counts) = java/util/stream/IntPipeline$3
@ 2 java.lang.invoke.LambdaForm$MH/1279902262::linkToTargetMethod (8 bytes) force inline by annotation
@ 4 java.lang.invoke.LambdaForm$MH/1847865997::identity (18 bytes) force inline by annotation
@ 14 java.lang.invoke.LambdaForm$DMH/2024969684::invokeStatic_L_L (14 bytes) force inline by annotation
@ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) force inline by annotation
@ 10 sun.invoke.util.ValueConversions::identity (2 bytes) inline (hot)
@ 7 java.util.stream.IntPipeline::reduce (16 bytes) inline (hot)
@ 3 java.util.stream.ReduceOps::makeInt (18 bytes) inline (hot)
@ 1 java.util.Objects::requireNonNull (14 bytes) inline (hot)
@ 14 java.util.stream.ReduceOps$5::<init> (16 bytes) inline (hot)
@ 12 java.util.stream.ReduceOps$ReduceOp::<init> (10 bytes) inline (hot)
@ 1 java.lang.Object::<init> (1 bytes) inline (hot)
@ 6 java.util.stream.AbstractPipeline::evaluate (94 bytes) inline (hot)
@ 50 java.util.stream.AbstractPipeline::isParallel (8 bytes) inline (hot)
@ 80 java.util.stream.TerminalOp::getOpFlags (2 bytes) inline (hot)
\-> TypeProfile (5122/5122 counts) = java/util/stream/ReduceOps$5
@ 85 java.util.stream.AbstractPipeline::sourceSpliterator (163 bytes) inline (hot)
@ 79 java.util.stream.AbstractPipeline::isParallel (8 bytes) inline (hot)
@ 88 java.util.stream.ReduceOps$ReduceOp::evaluateSequential (18 bytes) inline (hot)
@ 2 java.util.stream.ReduceOps$5::makeSink (5 bytes) inline (hot)
@ 1 java.util.stream.ReduceOps$5::makeSink (16 bytes) inline (hot)
@ 12 java.util.stream.ReduceOps$5ReducingSink::<init> (15 bytes) inline (hot)
@ 11 java.lang.Object::<init> (1 bytes) inline (hot)
@ 6 java.util.stream.AbstractPipeline::wrapAndCopyInto (18 bytes) inline (hot)
@ 3 java.util.Objects::requireNonNull (14 bytes) inline (hot)
@ 9 java.util.stream.AbstractPipeline::wrapSink (37 bytes) inline (hot)
@ 1 java.util.Objects::requireNonNull (14 bytes) inline (hot)
@ 23 java.util.stream.IntPipeline$3::opWrapSink (10 bytes) inline (hot)
\-> TypeProfile (4868/4868 counts) = java/util/stream/IntPipeline$3
@ 6 java.util.stream.IntPipeline$3$1::<init> (11 bytes) inline (hot)
@ 7 java.util.stream.Sink$ChainedInt::<init> (16 bytes) inline (hot)
@ 1 java.lang.Object::<init> (1 bytes) inline (hot)
@ 6 java.util.Objects::requireNonNull (14 bytes) inline (hot)
@ 13 java.util.stream.AbstractPipeline::copyInto (53 bytes) inline (hot)
@ 1 java.util.Objects::requireNonNull (14 bytes) inline (hot)
@ 9 java.util.stream.AbstractPipeline::getStreamAndOpFlags (5 bytes) accessor
@ 12 java.util.stream.StreamOpFlag::isKnown (19 bytes) inline (hot)
@ 20 java.util.Spliterator::getExactSizeIfKnown (25 bytes) inline (hot)
\-> TypeProfile (4870/4870 counts) = java/util/Spliterators$IntArraySpliterator
@ 1 java.util.Spliterators$IntArraySpliterator::characteristics (5 bytes) accessor
@ 19 java.util.Spliterators$IntArraySpliterator::estimateSize (11 bytes) inline (hot)
@ 25 java.util.stream.Sink$ChainedInt::begin (11 bytes) inline (hot)
\-> TypeProfile (4870/4870 counts) = java/util/stream/IntPipeline$3$1
@ 5 java.util.stream.ReduceOps$5ReducingSink::begin (9 bytes) inline (hot)
\-> TypeProfile (4871/4871 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 32 java.util.Spliterator$OfInt::forEachRemaining (53 bytes) inline (hot)
@ 12 java.util.Spliterators$IntArraySpliterator::forEachRemaining (68 bytes) inline (hot)
@ 53 java.util.stream.IntPipeline$3$1::accept (23 bytes) inline (hot)
@ 12 test.Measure$$Lambda$2/1745776415::applyAsInt (9 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = test/Measure$$Lambda$2
@ 5 test.Measure::lambda$setup$1 (4 bytes) inlining too deep
@ 17 java.util.stream.ReduceOps$5ReducingSink::accept (19 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 10 java.util.stream.IntPipeline$$Lambda$3/1779653790::applyAsInt (6 bytes) inlining too deep
\-> TypeProfile (1048064/1048064 counts) = java/util/stream/IntPipeline$$Lambda$3
@ 53 java.util.stream.IntPipeline$3$1::accept (23 bytes) inline (hot)
@ 12 test.Measure$$Lambda$2/1745776415::applyAsInt (9 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = test/Measure$$Lambda$2
@ 5 test.Measure::lambda$setup$1 (4 bytes) inlining too deep
@ 17 java.util.stream.ReduceOps$5ReducingSink::accept (19 bytes) inline (hot)
\-> TypeProfile (1048107/1048107 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 10 java.util.stream.IntPipeline$$Lambda$3/1779653790::applyAsInt (6 bytes) inlining too deep
\-> TypeProfile (1048064/1048064 counts) = java/util/stream/IntPipeline$$Lambda$3
@ 38 java.util.stream.Sink$ChainedInt::end (10 bytes) inline (hot)
@ 4 java.util.stream.Sink::end (1 bytes) inline (hot)
\-> TypeProfile (5120/5120 counts) = java/util/stream/ReduceOps$5ReducingSink
@ 12 java.util.stream.ReduceOps$5ReducingSink::get (5 bytes) inline (hot)
@ 1 java.util.stream.ReduceOps$5ReducingSink::get (8 bytes) inline (hot)
@ 4 java.lang.Integer::valueOf (32 bytes) inline (hot)
@ 28 java.lang.Integer::<init> (10 bytes) inline (hot)
@ 1 java.lang.Number::<init> (5 bytes) inline (hot)
@ 1 java.lang.Object::<init> (1 bytes) inline (hot)
@ 12 java.lang.Integer::intValue (5 bytes) accessor
26857 685 3 test.generated.Measure_multiply::multiply_avgt_jmhLoop (55 bytes)
@ 7 java.lang.System::nanoTime (0 bytes) intrinsic
@ 16 test.Measure::multiply (23 bytes)
@ 4 java.util.Arrays::stream (8 bytes)
@ 4 java.util.Arrays::stream (11 bytes)
@ 3 java.util.Arrays::spliterator (10 bytes)
@ 6 java.util.Spliterators::spliterator (25 bytes) callee is too large
@ 7 java.util.stream.StreamSupport::intStream (14 bytes)
@ 6 java.util.stream.StreamOpFlag::fromCharacteristics (37 bytes) callee is too large
@ 10 java.util.stream.IntPipeline$Head::<init> (8 bytes)
@ 4 java.util.stream.IntPipeline::<init> (8 bytes)
@ 4 java.util.stream.AbstractPipeline::<init> (55 bytes) callee is too large
@ 11 java.util.stream.IntPipeline::map (26 bytes)
@ 1 java.util.Objects::requireNonNull (14 bytes)
@ 8 java.lang.NullPointerException::<init> (5 bytes) don't inline Throwable constructors
@ 22 java.util.stream.IntPipeline$3::<init> (20 bytes)
@ 16 java.util.stream.IntPipeline$StatelessOp::<init> (29 bytes) callee is too large
@ 16 java.util.stream.IntPipeline::sum (11 bytes)
@ 2 java.lang.invoke.LambdaForm$MH/1279902262::linkToTargetMethod (8 bytes) force inline by annotation
@ 4 java.lang.invoke.LambdaForm$MH/1847865997::identity (18 bytes) force inline by annotation
@ 14 java.lang.invoke.LambdaForm$DMH/2024969684::invokeStatic_L_L (14 bytes) force inline by annotation
@ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) force inline by annotation
@ 10 sun.invoke.util.ValueConversions::identity (2 bytes)
@ 7 java.util.stream.IntPipeline::reduce (16 bytes)
@ 3 java.util.stream.ReduceOps::makeInt (18 bytes)
@ 1 java.util.Objects::requireNonNull (14 bytes)
@ 14 java.util.stream.ReduceOps$5::<init> (16 bytes)
@ 12 java.util.stream.ReduceOps$ReduceOp::<init> (10 bytes)
@ 1 java.lang.Object::<init> (1 bytes)
@ 6 java.util.stream.AbstractPipeline::evaluate (94 bytes) callee is too large
@ 12 java.lang.Integer::intValue (5 bytes)