3.  Android shipments reached 136 million
units in Quarter 3, 2012, which accounts for
75% of the 181.1 million shipments during
the quarter.
 Most of the Android powered device got a
3.5”-5” screen, 3G connectivity, Wi-
fi, Bluetooth, 1GHz or higher processor, GPS
and more, which powered by 1500 MAh
battery.

4.  We want to increase the battery life of the
smart devices but not to loose the
performance.
 Android is based on Linux kernel, we have
got the opportunity to modify the kernel, so
we choose this platform.

5.  Operating System
› Linux Mint for Compiling Source
 Tools
› Bash script
› Google’s updater script
› SQLite database engine

6.  Kernel governor and I/O scheduler
benchmark.
 init.d tweak
 GPS.conf tweak
 Build.prof tweak
 Odex and Deodex Rom
 zRAM swap and zipalign.
 SQLite auto sync off.

7.  Since Android/Linux is multitasking
capable, CPU needs to share its cycles to
more than one running task. This is a job for
CPU governor.
 Governors are especially important in smart
phones and tablets because they have a large
impact on the apparent fluidity of the
interface and the battery life of the device
over one time charge.

8.  Different governors have different
parameters. Ideally, a governor will have-
› Sampling rate
› Threshold
 Various tweak can be placed, and the
governor gives different battery
performance with due to various I/O
schedulers.

9.  Kernel controls the disk access using I/O
scheduler.
 Purpose of I/O scheduler:
› Minimize hard disk seek latency.
› Prioritize I/O requests from processes.
› Allocate disk bandwidth for running processes.
› Guarantee that certain requests will be served
before a deadline.

11.  Android boot-up process consists of the
following steps-
› At first the bootloader runs.
› Kernel boots and load various kernel objects(.ko
files) and prepare the hardware.
› User space programs are invoked. This is the
stage where the init.d script runs. Also various
apps and daemons are started to prepare the
Rom.

12.  Most of the custom kernel supports init.d
script.
 init.d script are to be placed inside
/system/etc/init.d directory (or
/etc/init.d which is a symbolic link to
/system/etc/init.d)
 Order of executing init.d scripts are in the
increasing order of ASCII values that
corresponds to their names.

14.  build.prop is a properties file of android
operating system.
 Battery performance can be improved by
changing build.prop properties like-
› Touch response
› 3G speed up
› Net speed tweak
› GPU rendering
› Wi-Fi signal tweak

15.  GPS.conf twaek
 Advertisement block
 SQLite auto synchronization off
 Odex and Deodex
 Zipalign
 zRAM swap