Android system uses a layered architecture, four layers:
1. Applicitations: Application Layer
2. Applicitation Framework: architectural layers
3. Libraries: library layer
4. Linux Kernel: Linux kernel layer
Implementation process:
Zygote three ways to create a process approach:
1. frok () to create a process Zygote
2. frokAndSpecialize () to create a non-Zygote process
3. frokSystemServer () to create a system service process
Description: Zygote process can create other processes frok (), after the child process also ended service system; non Zygote process is not
The Dalvik VM executes processes
Dalvik virtual machine JIT (time compilation, dynamic compilation)
Dalvik default compilation mode uses a trace
JIT compilation mode code comprises two bytes:
1. method: to function as a compilation unit
2. trace: a path for the compilation unit
a) trace into two categories
i thermal path: some functions are performed frequently performed
ii cold path: some functions are not performed frequently performed