主题：从曾经的Android组成员的角度来说说Android吧 -- zllwy

Android就是一个很普通的平台。

就是这个意思。

作为使用表形文字的民族，中国人从来都不缺想象力，虽然不从DJ“一树梨花压海棠”的某人，但个人还是觉得他的某些评论是对的。我们常常不能完成的，是将天马行空的假设，用严谨的逻辑证明出来，并以艰苦努力将其变成现实的物质成果。后两者，似乎是中国传统知识分子，所不擅长的。

是用Java开发的，所以需要一个Java VM, right?

Talking about VM, first thing hit my head is like VMware Fusion etc. Cannot understand why Android needs VM like that. A big misconception. :)

no MMU, what they really meant is no paging.

http://www.goland.org/whatiscosmos/

此人两年前在COSMOS工作过

呵呵，我们自己人也很喜欢它，敝帚自珍了。:P

I confused the JVM here with VMware kind of VM. :)

Something I googled out:

Up until Android 2.2 (Froyo) the JVM (really a Dalvik JVM for licensing reasons) on the Android platform was playing with one hand tied behind its back. Different from desktop/server Java, the JVM was still an interpreter, like the original JVM back in the Java 1.0 days. It was very efficient interpreter but an interpreter none-the-less and was not creating native code from the Dalvik bytecodes that it uses. As of Android 2.2 they have added a JIT, a just-in-time compiler, to the stack that translates the Dalvik bytecode into much more efficient machine code much like a C/C++ compiler. You can see the results of this in the benchmarks of Froyo which show a 2-5x improvement. As they add more and more JIT and GC features that have appeared in HotSpot, JRockit, etc, you will likely see even more improvements over time — without having to change or recompile the 3rd party developed software.

不知道你说的什么意思，是MMU without paging吗？我从来没见过这样的ARM实现。没有page，MMU保护什么呢？像x86一样的segment？

其实没有MMU的情况还是很多的。像Cortex Mx系列就没有MMU，从Cortex Ax开始才有。而且有时候为了performance，把MMU关掉也是有的。Linux里面有个CONFIG_MMU就是针对ARM的。不过看了一下我的phone上的/proc/config.gz，CONFIG_MMU=y。说明是turn on了。

他问了一堆的问题，很有意思。不过我很想知道这些问题最终的答案。大家都已经知道了Google的回答，MS总是太神秘了一点。

就是效率高低的问题了。

不是特别了解HBase，:)

至于Scope这一层，确实是更抽象的一层，可以架构在map/reduce基础上，也可以架构在bigtable基础上。

当然，语言的反驳是苍白的，且看事实的发展吧。