###############################################  power on till android lock screen comes up##  get information :#               --- cat /proc/bootprof#               --- [kernel hacking]  --> show timing information on printks  #  note :  dont remove the battery , the nand will rescanning the file system  #  BootRom#  Small piece of code that is hardwired in the CPU ASIC which preload#  preload#  uboot#  kernel+BSP driver#  nand mount (ubifs, yaffs, exit4)#  zygote pre-load class (almost constant time)#  package scanning  (increased with more apk number)#       --- packageManagerService开机启动扫描,管理所有的apk#       --- 不单单是获取图标的，还要记录每个应用的activity的主图标，数目，名称，权限 ......#  apk init time  (depends on setup apk) #  boot animation is a cpu consuming task ################################################ how to reduce the boot time#  preload  (make sure processor clock rate is set max )#  uboot #           ---Enable hardware ECC#           ---Remove unnecessary modules from u-boot.#           ---make sure that RAM timing values are adjusted properly so as to#               achieve optimal RAM throughput.#           ---Turn on I-Cache##  kernel  #          --- disable log #          --- improve the NAND throughput and the RAM throughput#          --- 修改内核img的打包方式，无压缩内核启动时间比较快，缺点是占用多一点的空间#  android #          --- moving to UBIFS file system can significantly reduce the boot up time#          --- reduce  apk  (the best way)#          --- decrease file numbers and size (less size , less loading time)#          --- reduce/remove the android pre-loading classes (but the side effect is that when start a app will slow )#          --- reduce the animation  (low fps , low size picture)#          --- 启动systemserver的时候，减少我们的service启动项,剔除我们不需要的一些service#               在后台持续运行的守护进程，不断的去读取binder设备，看有没有访问系统service的请求。#          ---#######################################################