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Mac OS X

Mac OS X. Scott Ferguson Section 1. Introduction. Background information on OS X Description of the OS X Architecture Mach Kernel Multithread Scheduling Memory Management Multiprocessing BSD-UNIX Components Networking File Systems Unix Security I/O Kit. OS X Overview.

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Mac OS X

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  1. Mac OS X Scott Ferguson Section 1

  2. Introduction • Background information on OS X • Description of the OS X Architecture • Mach Kernel • Multithread Scheduling • Memory Management • Multiprocessing • BSD-UNIX Components • Networking • File Systems • Unix Security • I/O Kit

  3. OS X Overview • 1997 Apple acquired NeXT, Inc. and their NextStep OS • Apple wanted to create an operating system with the power and efficiency of UNIX and the ease of use of the current Mac OS. • Apple release first version of OS X in 2001

  4. OS X Overview • In what environment is this OS designed to work? • Designed to be used only with Apple computers • Supports single and multiprocessor systems • Did this OS advance the state of the art? • Replaced “classic” Mac OS • Succeeded in making UNIX system easy to use

  5. OS X Overview • Is it commercially successful? • Mac OS holds about 3% of the current market share • What was done right/wrong? • High Quality Product • Frequent Updates

  6. OS X Architecture • The kernel is the core that provides basic services for the other parts of the operating system. • The Mac OS X kernel environment includes the Mach kernel, BSD-UNIX, the I/O Kit, file systems, and networking components.

  7. Kernel Environment

  8. Mach • Mach manages processor resources such as CPU usage, handles scheduling, provides memory protection, and provides a messaging-centered infrastructure to the rest of the operating-system layers. • The Mach component provides: • Inter-process communication (IPC) • remote procedure calls (RPC) • scheduler support for symmetric multiprocessing (SMP) • support for real-time services • virtual memory support

  9. Mach Scheduling • Mach scheduling is based on a system of run queues at various priorities that are handled in different ways. The priority levels are divided into four bands according to their characteristics

  10. Memory Management • Dynamically assigns memory to applications • Includes a fully-integrated virtual memory system that you cannot turn off • OS X does not use a pre-allocated swap partition for virtual memory. Instead, it uses all of the available space on the machine’s boot partition • Memory assigned to applications are protected from other memory segments, preventing conflicts and crashes

  11. Multiprocessing • OS X implements Multiprocessing by using SMP • Handles multiprocessor-ready applications by splitting the application into multiple independent threads, which the underlying operating system then schedules to run on multiple processors. • Automatically assigns threads/tasks to available processors in a way meant to maximize overall execution speed. • Uses “critical regions” to restrict access to a given shared memory range to one thread/task at a time. • Also, OS X provides semaphores for use as a synchronization mechanism among cooperating threads/tasks

  12. BSD • Above the Mach layer, the BSD layer provides advanced networking, security, and compatibility features • The BSD component provides • File systems • networking services • UNIX security model (user IDs and Permissions) • BSD Application Program Interfaces (APIs) • The system framework for exporting APIs to the application layers • Multi-user Access

  13. I/O Kit • The I/O Kit provides a framework for simplified driver development, that supports many categories of devices. • The I/O Kit component provides • dynamic device management • dynamic (“on-demand”) loading of drivers • power management for desktop systems as well as portables • multiprocessor capabilities

  14. Conclusions • Mac OS X provides a powerful UNIX-based operating system with an easy to use interface • The Kernel environment, which includes the Mach Kernel, the BSD-UNIX components, and the I/O kit, provide all of the needed services to the operating system (CPU, Memory Management, VM, Networking, Security) • The real success in OS X is that its Aqua GUI has managed to “hide” the UNIX from the user

  15. END

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