DistOS 2015W Session 4

Amoeba Operating System

Capablities:

• Pointer to the object
• Capability assigning right to perform to some operation to the object ticket
• Communicate wide area network
• a kind of ticket or key that allows the holder of the capa- bility to perform some (not neces- sarily all)
• Each user process owns some collection of capabilities, which together define the set of objects it may access and the types of operations that my ne performed on each
• After the server has performed the operation, it sends back a reply message that unblocks the client
• Sending messages, blocking and accepting forms the remote procedure call that can be encapsulate using to make entire remote operation look like local procedure
• Second field: used by the sever to identify which of its objects is being addressed server port and object number identify object which operation to performed
• Generates 48-bit random number
• The third field is the right field which contains a bit map telling which operation the holder of the capability may performed

Thread Management:

• Same process have multiple thread and each process has its own registered counter and stack
• Behave like process
• It can synchronized using mutex semaphore
• File: Multiple thread,
• Blocked when there's multiple threads
• Buttlet thread the mutex
• The careful reader may have noticed that user process can pull 813kbytes/sec

The V Distributed System

• First tent in V design: High Performance communication is the most critical facility for distributed systems.
• Second; The protocols, not the software, define the system.
• Third; a relatively small operating system kernel can implement the basic protocols and services providing a simple network-transparent process, address space & communication model.

Ideas that significantly affected the design

• Shared Memory.
• Dealing with group of entities same as they deal w/individual entities.
• Efficient file caching mechanism using the virtual memory caching mechanism.

Design Decisions

• Designed for a cluster of workstations with high speed network access ( only really supports LAN ).
• Abstract the physical architecture of the participating workstations, by defining common protocols providing well-defined interfaces.