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Operating System Concepts (2)

Module 2: Computer-System Structures.• Computer System Operation.• I/O Structure.• Storage Structure.• Storage Hierarchy.• Hardware Protection.• General System Architecture. 2.1 Silberschatz and Galvin 1999 Computer-System Architecture. 2.2 Silberschatz and Galvin 1999 Computer-System Operation.• I/O devices and the CPU can execute concurrently• Each device controller is in charge of a particular device type• Each device controller has a local buffer• CPU moves data from/to main memory to/from local buffers.• I/O is from the device to local buffer of controller• Device controller informs CPU that it has finished its operation by. causing an interrupt 2.3 Silberschatz and Galvin 1999 Common Functions of Interrupts.• Interrupts transfers control to the interrupt service routine. generally, through the interrupt vector, which contains the. addresses of all the service routines• Interrupt architecture must save the address of the interrupted. instruction• Incoming interrupts are disabled while another interrupt is being. processed to prevent a lost interrupt• A trap is a software-generated interrupt caused either by an error. or a user request• An operating system is interrupt driven 2.4 Silberschatz and Galvin 1999 Interrupt Handling.• The operating system preserves the state of the CPU by storing. registers and the program counter• Determines which type of interrupt has occurred:. – polling. – vectored interrupt system.• Separate segments of code determine what action should be. taken for each type of interrupt. 2.5 Silberschatz and Galvin 1999 Interrupt Time Line For a Single Process Doing Output. 2.6 Silberschatz and Galvin 1999 I/O Structure.• After I/O starts, control returns to user program only upon I/O. completion – wait instruction idles the CPU until the next interrupt. – wait loop (contention for memory access) – At most one I/O request is outstanding at a time, no. simultaneous I/O processing• After I/O starts, control returns to user program without waiting. for I/O completion – System call – request to the operating system to allow user. to wait for I/O completion – Device-status table contains entry for each I/O device. indicating its type, address, and state – Operating system indexes into I/O device table to determine. device status and to modify table entry to include interrupt. 2.7 Silberschatz and Galvin 1999 Two I/O methods.Synchronous Asynchronous. 2.8 Silberschatz and Galvin 1999 Device-Status Table. 2.9 Silberschatz and Galvin 1999 Direct Memory Access (DMA) Structure.• Used for high-speed I/O devices able to transmit information at. close to memory speeds• Device controller transfers blocks of data from buffer storage. directly to main memory without CPU intervention• Only one interrupt is generated per block, rather than the one. interrupt per byte 2.10 Silberschatz and Galvin 1999 Storage Structure.• Main memory – only large storage media that the CPU can. access directly• Secondary storage – extension of main memory that provides. large nonvolatile storage capacity• Magnetic disks – rigid metal or glass platters covered with. magnetic recording material. – Disk surface is logically divided into track