整数性能-x32与x64 jvm的30-50倍差异?

long ,但它的调用相当频繁-它的总使用量约占程序总时间的30-40%,而其他部分似乎“更重”。

我通常在x32jvm上运行不需要内存的程序,但是假设64位类型有问题,我尝试在x64jvm上运行同样的程序-‘livescenario’的总体性能提高了2-3倍。在这之后,我为特定方法的操作创建了JMH基准,并对x32和x64 jvm上的差异感到震惊-多达50次。

我会接受大约2倍慢的X32JVM(较小的字大小),但我没有任何线索,30-50次可能来自哪里。 你能解释清楚吗?

对评论的答复 :

• 我重写了测试代码来“返回一些东西”并避免了“死代码消除”—它似乎没有改变“x32”的任何东西,但是“x64”上的一些方法速度明显变慢了。
• 两个测试都是在“client”下运行的。在'-server'下运行没有明显的效果。

• “test code”是错误的:因为“没有返回值”,它允许JVM执行“死代码消除”或其他任何优化,而且“x32 JVM”所做的优化似乎比“x64 JVM”少,这导致了x32和x64之间的显著“错误”差异

以下是结果(注: ? 10?? 是否在Windows上没有打印特殊字符-它是用科学符号写成的,在0.001 s/op以下的字符,用10e-?)

x32 1.8.0_152

Benchmark                Mode  Score Units    Score (with 'return')
IntVsLong.cycleInt       avgt  0.035  s/op    0.034   (?x slower vs. x64)
IntVsLong.cycleLong      avgt  0.106  s/op    0.099   (3x slower vs. x64) 
IntVsLong.divDoubleInt   avgt  0.462  s/op    0.459
IntVsLong.divDoubleLong  avgt  1.658  s/op    1.724   (2x slower vs. x64)
IntVsLong.divInt         avgt  0.335  s/op    0.373
IntVsLong.divLong        avgt  1.380  s/op    1.399
IntVsLong.l2i            avgt  0.101  s/op    0.197   (3x slower vs. x64)  
IntVsLong.mulInt         avgt  0.067  s/op    0.068
IntVsLong.mulLong        avgt  0.278  s/op    0.337   (5x slower vs. x64)
IntVsLong.subInt         avgt  0.067  s/op    0.067   (?x slower vs. x64)
IntVsLong.subLong        avgt  0.243  s/op    0.300   (4x slower vs. x64)

x64 1.8.0_152

Benchmark                Mode  Score Units    Score (with 'return')
IntVsLong.cycleInt       avgt ? 10??  s/op   ? 10??
IntVsLong.cycleLong      avgt  0.035  s/op    0.034
IntVsLong.divDoubleInt   avgt  0.045  s/op    0.788 (was dead)
IntVsLong.divDoubleLong  avgt  0.033  s/op    0.787 (was dead)
IntVsLong.divInt         avgt ? 10??  s/op    0.302 (was dead)
IntVsLong.divLong        avgt  0.046  s/op    1.098 (was dead)
IntVsLong.l2i            avgt  0.037  s/op    0.067
IntVsLong.mulInt         avgt ? 10??  s/op    0.052 (was dead)
IntVsLong.mulLong        avgt  0.040  s/op    0.067
IntVsLong.subInt         avgt ? 10??  s/op   ? 10??
IntVsLong.subLong        avgt  0.075  s/op    0.082

这是(固定的)基准代码

import org.openjdk.jmh.annotations.Benchmark;

public class IntVsLong {

    public static int N_REPEAT_I  = 100_000_000;
    public static long N_REPEAT_L = 100_000_000;

    public static int CONST_I = 3;
    public static long CONST_L = 3;
    public static double CONST_D = 3;

    @Benchmark
    public void cycleInt() throws InterruptedException {
        for( int i = 0; i < N_REPEAT_I; i++ ) {
        }
    }

    @Benchmark
    public void cycleLong() throws InterruptedException {
        for( long i = 0; i < N_REPEAT_L; i++ ) {
        }
    }

    @Benchmark
    public int divInt() throws InterruptedException {
        int r = 0;
        for( int i = 0; i < N_REPEAT_I; i++ ) {
            r += i / CONST_I;
        }
        return r;
    }

    @Benchmark
    public long divLong() throws InterruptedException {
        long r = 0;
        for( long i = 0; i < N_REPEAT_L; i++ ) {
            r += i / CONST_L;
        }
        return r;
    }

    @Benchmark
    public double divDoubleInt() throws InterruptedException {
        double r = 0;
        for( int i = 1; i < N_REPEAT_L; i++ ) {
            r += CONST_D / i;
        }
        return r;
    }

    @Benchmark
    public double divDoubleLong() throws InterruptedException {
        double r = 0;
        for( long i = 1; i < N_REPEAT_L; i++ ) {
            r += CONST_D / i;
        }
        return r;
    }

    @Benchmark
    public int mulInt() throws InterruptedException {
        int r = 0;
        for( int i = 0; i < N_REPEAT_I; i++ ) {
            r += i * CONST_I;
        }
        return r;
    }

    @Benchmark
    public long mulLong() throws InterruptedException {
        long r = 0;
        for( long i = 0; i < N_REPEAT_L; i++ ) {
            r += i * CONST_L;
        }
        return r;
    }

    @Benchmark
    public int subInt() throws InterruptedException {
        int r = 0;
        for( int i = 0; i < N_REPEAT_I; i++ ) {
            r += i - r;
        }
        return r;
    }

    @Benchmark
    public long subLong() throws InterruptedException {
        long r = 0;
        for( long i = 0; i < N_REPEAT_L; i++ ) {
            r += i - r;
        }
        return r;
    }

    @Benchmark
    public long l2i() throws InterruptedException {
        int r = 0;
        for( long i = 0; i < N_REPEAT_L; i++ ) {
            r += (int)i;
        }
        return r;
    }

}