Android 5.0 , Lollipop

Android 5.0 LollipopA Sweet new take

on Android. It is the latest version of the Android mobile operating system developed by Google.

Unveiled on June 25,2014 and its source code was made available on November 3, 2014.

Platforms – Android TV , Android auto , Wearable Platforms like Android wear and Fitness bands.

Lollipop VS Kit Kat

Redesigned user interface built around a responsive design language referred to as "material design“.

Internal changes were also made to the platform, with the Android Runtime (ART) officially replacing Dalvik for improved application performance.

Advanced Notification System. Changes intended to improve and optimize battery usage, known

internally as Project Volta. Added Security features – Geo lock

Kernel Structure

based on the Linux kernel, a monolithic kernel.

Linux kernel supports true preemptive multitasking (both in user mode and kernel mode), virtual memory, shared libraries, demand loading, shared copy-on-write executables (via KSM), memory management, the Internet protocol suite, and threading.

Written in c language

Has a GCC compiler.

Has several flash storage partitions like /System for operating system itself and /data for installing applications.

Users not given root access to these sensitive areas , but security flaws can be violated.

On top of the Kernel , it has all libraries,middlewares and API’s wriiten in c,running on application frameworks.

Drivers are loaded as modules , loading and unloading when needed.

Includes java compatible libraries based on apache harmony.

It uses dalvik or ART runtime environments.

Uses Bionic instead of GNU C library – different licencing model , Smaller runtime footprint , Optimization for lower frequency CPUs.

Memory Management

Android uses its own run time and virtual machine to manage application memory.

Manages process lifetimes.

Ensures application responsiveness by stopping and killing processes as necessary to free resources for higher priority applications.

Each application runs in a sandbox, has its own resources .

Dalvik and ART ensures memory management.

Application priority and Process states

Scheduling Algorithm

Different workloads , So Using a particular scheduling algorithm for all is difficult.

Provides Preemptive scheduling under certain critical conditions. Preemption improves latency , responsiveness. Uses Completely Fair Scheduler by default.

Uses 2 real time scheduling classes SCHED-FIFO SCHED-RR

RR between queues

Timeslice for each queue ( RR gets 80% , FCFS gets 20%)

Introduced in kernel 2.6.23 Models an ideal multitasking CPU.

Infinitesimally small timeslice. N processes : each progresses uniformly at 1/n’th rate.

Completely Fair Scheduler

Completely Fair Scheduler

Problem : real CPU cant be split into infinitesimally small timeslice without excessive overhead.

Core Ideas : dynamic time slice and order. Don’t use fixed time slice per task.

Instead , dynamic time slice across all tasks. Scheduling latency.

Don’t use round robin to pick next task. Pick task which has received least CPU time so far Equivalent to dynamic priority.

Thank You

By:P.Jagadeesh.