我有一个界面PackedObject
:
public interface PackedObject {
int get();
int sum();
void setIndex(int index);
default int defaultSum() {
return get();
}
}
抽象类AbstractPackedObject
:
public abstract class AbstractPackedObject implements PackedObject {
protected int index = 0;
protected int[] buffer;
public void setIndex(int index) {
this.index = index;
}
public void setBuffer(int[] buffer) {
this.buffer = buffer;
}
@Override
public int sum(){
return get();
}
}
以及具体的实现WrappedPackedObject
:
public class WrappedPackedObject extends AbstractPackedObject implements PackedObject {
public WrappedPackedObject(int[] buffer) {
this.buffer = buffer;
}
@Override
public int get() {
return buffer[index];
}
}
我进行了基准测试defaultSum
and sum
方法(JMH 基准的片段):
for (int i = 0; i < NB; i++) {
packedObject.setIndex(i);
value += packedObject.defaultSum();
}
for (int i = 0; i < NB; i++) {
packedObject.setIndex(i);
value += packedObject.sum();
}
我试图弄清楚为什么sum
基准测试仪比defaultSum
基准指数提高了 1.7 倍。
我已经开始深入研究 JIT 的奥秘。调用站点仅针对一种方法,因此我希望完成内联。打印内联的输出如下:
@ 25 com.github.nithril.PackedObject::defaultSum (7 bytes) inline (hot)
\-> TypeProfile (479222/479222 counts) = com/github/nithril/WrappedPackedObject
@ 1 com.github.nithril.WrappedPackedObject::get (14 bytes) inline (hot)
@ 10 java.nio.DirectByteBuffer::getInt (15 bytes) inline (hot)
@ 25 com.github.nithril.AbstractPackedObject::sum (5 bytes) inline (hot)
@ 1 com.github.nithril.WrappedPackedObject::get (14 bytes) inline (hot)
@ 10 java.nio.DirectByteBuffer::getInt (15 bytes) inline (hot)
我还不明白为什么会出现这一行TypeProfile (479222/479222 counts) = com/github/nithril/WrappedPackedObject
我创建一个专用项目 https://github.com/nithril/packedobject-test与上面的代码。基准测试是使用 JMH 完成的。
感谢您的帮助。
编辑2015/05/20:
我简化了java代码。
的内循环benchSum
非常简单:
0x00007f1bb11afb84: add 0x10(%r10,%r8,4),%eax ;*iadd
; - com.github.nithril.PackedObjectBench::benchSum@29 (line 50)
0x00007f1bb11afb89: mov %r8d,0xc(%r12,%r11,8) ;*putfield index
; - com.github.nithril.AbstractPackedObject::setIndex@2 (line 13)
; - com.github.nithril.PackedObjectBench::benchSum@17 (line 49)
0x00007f1bb11afb8e: inc %r8d ;*iinc
; - com.github.nithril.PackedObjectBench::benchSum@31 (line 48)
0x00007f1bb11afb91: cmp $0x2710,%r8d
0x00007f1bb11afb98: jl 0x00007f1bb11afb84
的内循环benchDefaultSum
索引的读/写以及内部循环内数组绑定的比较更加复杂。我还没有完全理解这种比较的目的......
0x00007fcfdcf82cb8: mov %edx,0xc(%r12,%r11,8) ;*putfield index
; - com.github.nithril.AbstractPackedObject::setIndex@2 (line 13)
; - com.github.nithril.PackedObjectBench::benchDefaultSum@17 (line 32)
0x00007fcfdcf82cbd: mov 0xc(%r10),%r8d ;*getfield index
; - com.github.nithril.WrappedPackedObject::get@5 (line 17)
; - com.github.nithril.PackedObject::defaultSum@1 (line 15)
; - com.github.nithril.PackedObjectBench::benchDefaultSum@24 (line 33)
0x00007fcfdcf82cc1: cmp %r9d,%r8d
0x00007fcfdcf82cc4: jae 0x00007fcfdcf82d1f ;*iaload
; - com.github.nithril.WrappedPackedObject::get@8 (line 17)
; - com.github.nithril.PackedObject::defaultSum@1 (line 15)
; - com.github.nithril.PackedObjectBench::benchDefaultSum@24 (line 33)
0x00007fcfdcf82cc6: add 0x10(%rcx,%r8,4),%eax ;*iadd
; - com.github.nithril.PackedObjectBench::benchDefaultSum@29 (line 33)
0x00007fcfdcf82ccb: inc %edx ;*iinc
; - com.github.nithril.PackedObjectBench::benchDefaultSum@31 (line 31)
0x00007fcfdcf82ccd: cmp $0x2710,%edx
0x00007fcfdcf82cd3: jl 0x00007fcfdcf82cb8 ;*aload_2
[...]
0x00007fcfdcf82ce6: mov $0xffffffe4,%esi
0x00007fcfdcf82ceb: mov %r10,0x8(%rsp)
0x00007fcfdcf82cf0: mov %ebx,0x4(%rsp)
0x00007fcfdcf82cf4: mov %r8d,0x10(%rsp)
0x00007fcfdcf82cf9: xchg %ax,%ax
0x00007fcfdcf82cfb: callq 0x00007fcfdcdea1a0 ; OopMap{rbp=NarrowOop [8]=Oop off=416}
;*iaload
; - com.github.nithril.WrappedPackedObject::get@8 (line 17)
; - com.github.nithril.PackedObject::defaultSum@1 (line 15)
; - com.github.nithril.PackedObjectBench::benchDefaultSum@24 (line 33)
; {runtime_call}
0x00007fcfdcf82d00: callq 0x00007fcff1c94320 ;*iaload
; - com.github.nithril.WrappedPackedObject::get@8 (line 17)
; - com.github.nithril.PackedObject::defaultSum@1 (line 15)
; - com.github.nithril.PackedObjectBench::benchDefaultSum@24 (line 33)
; {runtime_call}
[...]
0x00007fcfdcf82d1f: mov %eax,(%rsp)
0x00007fcfdcf82d22: mov %edx,%ebx
0x00007fcfdcf82d24: jmp 0x00007fcfdcf82ce6