1 Advanced Operating Systems - Fall 2009 Lecture 2 – January 12, 2009 Dan C. Marinescu Office: HEC 439 B

2 Class organization (cont’d) Class webpage: References: “Operating system concepts” by Silberschatz, Gavin, Gagne Selected papers. Office hours: M, Wd, 3:00 – 4:30 PM

3 Last, Current, Next Lecture Last time: “The Big Picture” Today: The relationship between physical systems and models Layering Virtualization. Next time: Operating Systems Structures

4 Physical Organization Processor Main memory Auxiliary processors (channels, graphics cards, etc.) Secondary storage (disks) I/O devices Busses Common bus, Memory bus, USB

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6 Processors Clock rate: < 3 GHz Multiple functional units: integer, floating point, pixel. Performance: MIPS, Mflops L1 Cache Registers Different architectures Instruction set RISC, CISC (Intel) Multi-core Memory-mapped I/O

7 Processor support for OS functions Instructions supporting atomic operations: Load and Test, Swap Multiple execution modes: at least two Kernel User Clock and Timers Interrupts Memory management support: paging and segmentation.

8 Auxiliary processors Channel I/O  a high-performance input/output (I/O) architecture implemented with a custom processor, known as peripheral processor, I/O processor, I/O controller, or DMA controller.input/output I/O Controller Hub (ICH) Intel 82801, an Intel microchip used on motherboards with Intel chipsets. ICH10 southbridge (June 2008) with the Intel P45.motherboardschipsetsIntel P45 Graphic cards  transform binary images into pixels that can be displayed on the screen. Main components: A motherboard connection for data and powermotherboard A processor to decide what to do with each pixel on the screenprocessor Memory to hold information about each pixel and to temporarily store completed pictures. Memory A monitor connection.monitor How will the multi-cores change this?

9 Storage Hierarchy

10 Storage Attributes

11 Basic concepts Abstractions and models. Universal computers. Resource virtualization. Concurrency. Physical Systems State of a system, a process, a computation.

12 The role of abstractions Identify problems which require a solution: Physical devices operate at different speeds. Resource sharing. Separate logical (conceptual) principles from the physical (practical) implementation. Define logical structures that capture the properties of diverse physical systems.

13 Abstractions Processes and Threads  abstract programs in execution. Pages and Segments  support memory management. Caching  reduce the gap between memory access time and instruction execution time. Multitasking  hide the gap between the speed of processors and I/O devices. Spooling  simultaneous peripheral operations on-line Critical Section  support resource sharing. Windows  GUI for user-computer interactions

14 Abstractions versus physical reality Physical properties of systems play an important role: Speed Volume/quantity Physical dimensions Power consumption Reliability Time  difficult to deal in programming models and abstractions.

15 Models Retain the “relevant” properties of a system. Examples: Service-oriented OS: different functions implemented as services and available through system calls. The Internet is based upon the “best-effort” model Layered models – separation of functions; each layer communicates only with the adjacent ones. Layered model of the OS Communication architecture

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17 Virtualization Techniques to: facilitate the development of portable software (JVM); overcome physical limitations of the components of systems; provide uniform access to a distributed, heterogeneous, distinct, or non-uniform, collection of resources. A virtual resource management system is typically a layer of software and the associated hardware support to map virtual to physical resources. For example: Virtual memory allows uniform, contiguous addressing of physically separate and non-contiguous memory and secondary storage areas. Virtual memory was developed around 1958 at the University of Manchester for the Atlas computer; all modern operating systems have a memory management system mapping virtual address spaces of several Gbytes to a physical memory of different size. Software implementations of different types of RAID (Redundant Arrays of Inexpensive Disks) are supported by many operating systems including Microsoft's server operating systems and the Mac OS X Server. Has the potential to increase system vulnerability

18 Virtual Machines The resources of the physical computer are shared to create the virtual machines CPU scheduling can create the appearance that users have their own processor Spooling and a file system can provide virtual card readers and virtual line printers Windows A normal user time-sharing terminal serves as the virtual machine operator’s console

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20 VMware Architecture