Android 其实没有对Linux Kernel做太多的改变 （大多数改变都是通过device driver
// kernel module）
list of the changes made to the Linux kernel:
1) ashmem (Android Shared Memory), a file-based shared memory system.
2) Binder, an inter-process communication (IPC) and remote procedure call (
RPC) system.
3) logger, a high-speed in-kernel logging mechanism optimized for writes.
4) Paranoid Networking, a mechanism to restrict network I/O to certain
processes.
5) pmem (Physical Memory), a driver for mapping large chunks of physical
memory into user-space.
6) Viking Killer, a replacement OOM killer that implements Android's "kill
least recently used process" logic under low memory conditions.
7) wakelocks, Android's unique power management solution, in which the
default state of the device is sleep and explicit action is required (via a
wakelock) to prevent that
8）再加上一些driver for architecture
要说越用越慢，user level的App是罪魁祸首的机会更大(abusively using kernel)，
不要什么软件都装(搞不好没有节制的使用pmem和wakelocks)，尤其是一些国内软件
