Mach Kernel
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Mach is an object-oriented operating system kernel. It defines basic abstractions like tasks, threads, ports, and memory objects. Tasks provide execution environments, threads are units of execution, ports enable communication between tasks using messages, and memory objects are sources of shared memory. Tasks communicate asynchronously through message passing to ports using the mach_msg system call.
Mach Kernel
- 1. Mach Kernel 4/9/2013 arifch2009@gmail.com
- 2. • Mach is object-oriented system. • Data and the operations that manipulate that data are encapsulated into an abstract object.. • The details of how these operations are implemented are hidden, as are the internal data structures. • Use of an object is done by invoking its defined • It allows objects to reside anywhere in a network of Mach systems, transparent to the user. 4/9/2013 arifch2009@gmail.com
- 3. Mach’s basic abstractions 4/9/2013 arifch2009@gmail.com
- 4. • Task : A task is an execution environment , a traditional process would be implemented as a task with a single thread of control. – May have multiple thread. – Resources : Address Spaces, Threads, Port rights, ports sets, local name spaces. – task_create(parent_task, inherit_memory, child_task) • Thread : is the basic unit of execution and must run in the context of a task (which provides the address space). – All threads within a task share the tasks’ resources (ports, memory, and so on). – The threads belonging to a single task can execute in parallel at different processors in a shared-memory multiprocessor. – thread_create(parent_task, child_thread) – thread_set_state(thread, flavour, new_state, count) – Thread_resume(thread) 4/9/2013 arifch2009@gmail.com
- 5. • Port : is a unicast, unidirectional communication channel with an associated message queue. – a task must have a port right to send a message to a port. – Communication is accomplished by sending messages to ports. – messages are queued at the destination port if no thread is immediately ready to receive them. • Port Set : Set of ports treated as a single unit when receiving a message. – They share a common message queue. – Each received message identifies the individual port 4/9/2013 arifch2009@gmail.com
- 6. • Messages : is the basic method of communication between threads in Mach. – Contain Message header. – It is a typed collection of data objects. – Port rights are passed in messages; • Memory object : is a source of memory; tasks can access it by mapping portions of an object (or the entire object) into their address spaces. 4/9/2013 arifch2009@gmail.com
- 7. Communication Model • Ports are the channel where communication occurs by sending message to ports. • Mach provides a single system call for message passing: mach_msg mach_msg(msg_header, option, snd_siz, rcv_siz, rcv_name, timeout, notify) 4/9/2013 arifch2009@gmail.com
- 8. • The header is composed of: – Port destination. – Answer port. – Operation identifier. – Size of the data list. 4/9/2013 arifch2009@gmail.com
- 9. 4/9/2013 arifch2009@gmail.com
Editor's Notes
- #8: In a request/response messaging pattern, one party sends a request message and the receiving party returns a response message. Two typical examples of request/response processing are the interaction that a browser has with a Web server using the HTTP adapter, and Web service processing using the Simple Object Access Protocol (SOAP) adapter