a toy virtual machine project

Project BackgroundProject Scope

Project Achievements

Virtual Machine Project

Presented by Yan Dacong

School of Software, SJTU

September 25, 2008

Yan Dacong, Zhang Xuchao, Duan Beichen Virtual Machine Project



Agenda

1 Project Background

2 Project Scope

3 Project Achievements




Project Background




Why study virtual machines?

Ubiquitous Applications

Personal & CommercialDesktop & Workstation

Challenging & Exciting

Operating System CompatibilityComputer Architecture Compatibility

Promising future

Trend: servers much stronger computation abilityMake full use via VM Technology




Project Scope

What we are doing in this PRP:

Get acquaintance with basic concepts of virtual machinesAcquire familiarity with applications of virtual machinesMaster the basic techniques of virtual machine implementationDevelop a process virtual machine for MIPS

What we are NOT doing in this PRP:

Implement a full-scale system virtual machineDevelop a brand-new virtual machine model




Project Achievenments

Categories of VM

Instruction Emulation

MIPS Process Virtual Machine




Categories of VM

System Virtual Machine (SVM)

First developments: 1960s 1970sComplete system enrionmentsRun apps simultaneously on multiple platformsTypical Products: VirtualBox, VMWare

Process Virtual Machine (PVM)

Simpler modelRule out platform differencesRun apps written in different ISAsTypical Products: JVM, SPIM




Figure 1: A taxonomy of Virtual Machines




Instruction Emulation

Interpretation

Easy to implementEfficiency bottleneck

Binary Translation

Speed up, esp. for hotspot codesSlow startup

Hybrid Approach

Combine the previous twoSelect proper strategies at run-time




Figure 2: Basic steps of instruction emulation




MIPS Process Virtual Machine

Programme Loader

Predecoding Interpretation

Table-Driven Execution




Figure 3: Process Layout




MIPS Instruction Format

I-Type(Immediate)

J-Type(Jump)

R-Type(Register)




Figure 4: MIPS Instruction Format




Table-Driven Execution

Switch-loop is suboptimal!

Figure 5: Switch Loop Approach




Table-Driven Execution(Cont.)

Table-Driven Approach is Better!

(a) Execution Function Table (b) Instruction Execution

Figure 6: Table-Driven Execution




Conclusion

VM is a promising field

VM is worth studying

VM would have an even wider application




Thank you!
