Android 是否阉割了 ARM 的 Jazelle 技术? [英] Does Android castrate the ARM's Jazelle technology?

问题描述

我所看到的我们是否应该说混蛋"Android 中的 Java 字节码的理由是性能.(我怀疑还有另一个原因.)但是，通过更改字节码，他们是否没有使 Jazelle 等硬件加速技术没有实际意义，从而实际上降低了可用于 Mobile Java 平台的性能?

The justification that I've seen for shall we say "Bastardizing" the Java bytecodes in Android was performance. (I suspect there is another reason.) However by changing the byte codes haven't they made hardware acceleration technologies such as Jazelle moot, and thus actually degraded the performance available for a Mobile Java platform?

知道目标平台是基于 ARM 的移动平台，这对我来说似乎有违直觉.虽然它可能会在其他 CPU 架构上为您提供更好的性能，但它似乎在 ARM 和 Jazelle 面前吐槽.

It appears counter intuitive to me knowing that the target platform is a ARM based mobile platform. While it MIGHT give you better performance on other CPU architectures it seems to spit in the face of ARM and Jazelle.

它对 Java 性能有什么样的量化影响?

What sort of quantitative effect does it have on Java performance?

它真的能提高性能吗?如果能，效果如何?

Does it actually improve performance, and if so how?

对其他平台有什么影响?(即 x86、mips、yadda、yadda、yadda...)

What's the effect on other platforms? (i.e. x86,mips,yadda,yadda,yadda...)

推荐答案

是的 Dalvik 让 Jazelle 变得毫无用处.唯一的问题是 Jazelle 开始有用还是 90% 的营销炒作?一个好的 JIT 或 AOT(ahead of Time) 编译器往往比尝试使用专门的指令提供更好的性能.Dalvik 基于寄存器的方法可能比传统的 java 字节码解释器更快，但如果解释器和 JIT 之间的差异很小.希望 Android 的下一个版本之一具有 JIT.

Yes Dalvik makes Jazelle useless. The only question is was Jazelle useful to begin with or is it 90% marketing hype? A good JIT or AOT(ahead of Time) compiler tends to give much better performance than trying to use specialized instructions. The register based approach of Dalvik might be faster than a traditional java bytecode interpreter but if the difference in minor between that of an interpreter and that of a JIT. Hopefully one of the next versions of Android has a JIT.

用最先进的垃圾收集器和优化器编写一个好的虚拟机需要大约 5-10 年的时间.Sun(和微软)已经度过了那些年.谷歌没有.希望他们会继续投资，以便有一天 Android Java 代码不会比应有的速度慢 90%.

It takes ~5-10 years to write a good virtual machine with state of the art garbage collectors and optimizers. Sun (and Microsoft) have spent those years. Google hasn't. Hopefully they will keep investing in it so that one day Android Java code isn't a 90% slower than it should be.

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