Comparison of Amoeba, Mach and Chorus

Presented By Er. Shiva K. Shrestha (15957)DOS, ME ComputerNepal College of Information Technology

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Amoeba DOS

Times Sharing DOS Based on Microkernel Execution Model: Pool Processor Automatic Load Balancing Automatic File Replication Object Based DSM Used Main Objectives:

Distribution, Parallelism, Transparency, Performance

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Amoeba System Architecture

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Amoeba Microkernel

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Process managementMemory managementCommunicationI/O

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Key Concepts of Amoeba

Microkernel Remote Procedure Calls (RPC) Threads FLIP Objects Capability Various Servers

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Mach DOS

Designed for 1 CUP/Multiprocessor Extensive Multiprocessor Support Maximum No. of Kernel Calls: 153 Memory Mapped Objects Integrated Memory Mgmt. Page Based DSM No Group Communication

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Mach Principal Abstractions

Processes Threads Memory Objects Ports Messages

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Process Mgmt. in Mach

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Monolithic Vs. Microkernel

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Chorus DOS

Microkernel Based RTOS Flexible Virtual Memory

Implementation Binary Level OS Emulation Async. Communication Page Based DSM Optimized for Local Case

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Chorus Chief Design Features Dynamically Loadable Servers Enhancement of Unix Server Group & Reconfiguration Distributed Memory Multiprocessor

Operations Real-time Operations

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Conclusion (1)

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ITEM AMOEBA MACH CHORUSDesigned for: Distributed system 1 CPU, multiprocessor 1 CPU, multiprocessor

Execution model Pool processor Workstation Workstation

Microkernel? Yes Yes Yes

Number of kernel calls 30 153 112

Automatic load balancing?

Yes No No

Capabilities General Only ports General

Capabilities in: User space Kernel User space

Threads managed by: Kernel Kernel Kernel

Transparent heterogenity?

Yes No No

User-settable priorities? No Yes Yes

Multiprocessor support Minimal Extensive Moderate

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Conclusion (2)

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ITEM AMOEBA MACH CHORUSMapped object Segment Memory object SegmentDemand paging? No Yes YesCopy on write? No Yes YesExternal pagers? No Yes YesDistributed shared memory

Object based Page based Page based

RPC? Yes Yes YesGroup communication Reliable, ordered None Unreliable

Asynchronous communication?

No Yes Yes

Intermachine messages Kernel User space/kernel Kernel

Messages address to: Process Port PortUNIX emulation Source Binary BinaryUNIX compatibility POSIX (partial) BSD System VSingle-server UNIX? No Yes NoMultiserver UNIX? Yes No YesOptimized for: Remote case Local case Local caseAutomatic file replication? Yes No No

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Questions?

Thank You !

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