android启动优化

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#  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 
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# 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。
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