GREENDROID: EXPLORING THE NEXT EVOLUTION IN SMARTPHONE APPLICATION

PROCESSOR

CONTENTS

Technology Problem Statement. Basic definition involved. Proposed Schemes. Design Goals. Architectures. Methodology. Result. Future Enhancement. Conclusion.

TECHNOLOGY

This study is mainly for smart phone application processor. Smartphone applications' energy efficiency is vital, but many Android applications suffer from serious energy inefficiency problems . So Greendroid is discussed to eradicate this problem and make the processors energy efficient.

PROBLEMS IN THE SMARTPHONE PROCESSOR

Exponentially worsening problem is “DARK SILICON “ to be the primary force that dictates the evolution in the processor.

Dark Silicon Age kicked off with the transition to multi core. For every new generation of process the percentage of the transistors that a chip can switch at full frequency is dropping exponentially due to power constraints

UTILIZATION WALL

Utilization wall dictates that due to poor CMOS scaling, improvements in processor performance are determined not by improvements in transistor frequency or transistor count, but rather by the degree to which each process shrink reduces the switching energy for underlying transistors.

BASIC DEFINITIONS

TRANSISTORS : A transistor is a semiconductor device used to amplify and switch electronic power and signals.

MICROPROCESSOR : The microprocessor is a programmable device that accepts digital data as input, processes it ,stored in its memory, and provides results as output .

MULTICORE : A multi-core processor is a single computing

component with two or more independent actual processing units which are the units that read and execute program instructions.

SILICON : A small piece of semiconducting material on which integrated circuit is embedded.

PROPOSED SCHEMES

C-cores.

Greendroid.

MOORE’S LAW

The observation that, over the history of computing hardware, the “number of transistors in a dense integrated circuit doubles approximately every two years”.

DESIGN GOALS

Low complexity. Easy of integration . Capability. Utilization wall is a fundamental first order constraint for processor design.

to predict this CMOS scaling theory is used. The architectures needed to be created that can leverage many transistors

without actually actively switching them all.

GREENDROID ARCHITECTURE

Greendroid processor combines general purpose processor with application specific processor that are very efficient.

Greendroid is a heterogeneous tiled architecture. The tiles caches are kept coherent through a simple cache coherence schemes that allows caches of inactive tiles to be collectively used .

Greendroid tiles however are not uniform each of them contain unique collection of 8 to 15 cores.

Android : Green droid's Target Workload.

Android is an excellent target for Greendroid-Style Architecture.

Android comprises of three main components Linux kernel, a collection of native libraries and Dalvik virtual machine.(DVM)

Android’s usage model also reduces the need for the patching in architecture.

This architecture also includes a mesh-based on-chip network.

Conservation Cores

It is known as C-Cores specialized coprocessors.

C-cores are a post –multicore approach that constructively reduces the energy consumption of an application by 10x or more.

These cores target specific Android hotspots, including the kernel.

C-cores concept by applying the technique to the Android mobile software stack in order to build a mobile application processor that runs the applications with a fraction of the energy consumption..

LIFE CYCLE

C-cores are paired with energy efficient general purpose host CPU and perform all their memory operations through data cache.

Frequently executed hot code regions are implemented using C-cores while cold regions are executed on the host CPU.

C-cores generally have slight improvements in performance versus general purpose cores. They can have up to 18x improvement in energy efficiency.

GENERATION OF C-Core

It is relatively a straight forward process . It is parallelism and regularity-agnostic and employs a function call.

Passes through compiler which code reconstitution. Supports CFG’s ,data structures and arbitrary memory access patterns etc. After code is been reshaped then respective control flow diagrams and

data flow diagrams are drawn for respective process. Each instruction in the basic block is directly converted into hardware

operator. The live-ins of the DFD’s are turned into register. The control logic is

created control logic that sequences the multiplexed operators and stalls the sequencing logic appropriately on a cache miss. This logic represented by using Verilog.

METHODOLGY GREENDROID To reduce the energy consumption a mobile application processor is introduced. It serves as an prototype for mobile application processor. Greendroid is research prototype that demonstrates the use of cores that saves energy across the hotspots in the Android mobile phone software stack. A single Greendroid processor will contain tens or hundreds of different cores that each implement a different key function in Android. Greendroid attacks one of the most important realities of Moore’s Law.

SYNTHESIZING C-CORES FOR GREEENDROID

C-core tool chain converts arbitrary c functions into C-core hardware. This tool chain targets a much wider range of C constructs and build

energy saving C-cores for functions that are poor targets for acceleration. The tool chain’s profiling pass identifies “hot” functions and loops in the

target workload and isolates them by in lining functions and outlining loops.

The data path mirrors the single static assignment program representation the compiler uses internally and groups instruction together by basic block.

The control path tracks the execution through function with a state machine that closely matches the function’s control flow graph .

Ctnd.. The compiler also generates function stubs to replace the original

functions by invoking the hardware. C-cores support this by providing targeted reconfigurability that lets them

to maintain perfect fidelity to changing source code. C-cores provide built-in support for changes to compile-time constants as

well as general mechanism for transferring the control back to core to execute the individual basic block.

RESULT

GreenDroid leverage "dark silicon" to dramatically reduce energy consumption by integrating conservation cores in smartphone .C-cores also incorporate focused reconfigurability that allows them to adapt to small changes in the target application while still realizing efficiency gains.

Future Scope

“Turbo mode “that runs some cores faster if others are switched off. We can expect similar trends for future of mobile processors as well.

CONCLUSION

The severity of the problem is to develop new architectural tradeoffs that trade Dark Silicon , an exponentially cheapening resource ,for energy which is the true limiter of performance today. Conversation cores and Greendroid offers potential way to attack the Dark silicon problem.