Lecture8 - COP 4600 Operating Systems Fall 2010 Click to...

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Click to edit Master subtitle style 8/1/11 Lecture 8 COP 4600 Operating Systems Fall 2010 Dan C. Marinescu Office: HEC 439 B Office hours: Tu-Th 3:30-4:30 PM
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Lecture 8 8/1/11 n Last time: n Use by: value/name. Binding and indirection n Generic naming model n Practical design of naming scheme ¨ Contexts ¨ Name overloading n Today n Computer System Organization. Hardware and software modules. ¨ Optimization. DMA, memory mapped I/O. ¨ The file abstraction. n UNIX File System n User-friendly names – Case Study URLs n Next time ¨ Soft modularity Lecture 8 – Thursday September 16, 2010 22
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Lecture 8 8/1/11 Figure 2.16 from the textbook 33
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Lecture 8 8/1/11 44 Figure 2.17 from the textbook
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Lecture 8 8/1/11 Optimization n Direct Memory Access (DMA): ¨ supports direct communication between processor and memory; the processor provides the disk address of a block in memory where data is to be read into or written from. ¨ hides the disk latency; it allows the processor to execute a process while data is transferred n Memory Mapped I/O: ¨ LOAD and STORE instructions access the registers and buffers of an I/O module n bus addresses are assigned to control registers and buffers of the I/O module n the processor maps bus addresses to its own address space (registers) ¨ Supports software functions such as UNIX mmap which map an entire file. n Swap area: disk image of the virtual memory of a process. 55
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Lecture 8 8/1/11 DMA Transfer 6 66
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Lecture 8 8/1/11 B. The software layer: the file abstraction n File: memory abstraction used by the application and OS layers ¨ linear array of bits/bytes ¨ properties: n durable 7 information will not be changed in time n has a name ” n which defines the current position in the file. n The OS provides an API (Application Programming Interface) supporting a range of file manipulation operations. n A user must first OPEN a file before accessing it and CLOSE it after it has finished with it. This strategy: ¨ allows different access rights (READ, WRITE, READ-WRITE) ¨ coordinate concurrent access to the file n Some file systems ¨ use OPEN and CLOSE to enforce before-or-after atomicity ¨ support all-or-nothing atomicity & e.g., ensure that if the system crashes before a CLOSE either all or none of WRITEs are carried out 77
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Lecture 8 8/1/11 Open and Read operations 8 88
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Lecture 8 8/1/11 Unix and Unix File System n Developed in early 1970s at Bell Labs for PDP computers made by Digital n n Versions: ¨ Berkeley Unix (BSD) ¨ GNU/Linux ¨ Darwin – part of MAC OS n Unix file system – hierarchical data organization: blocks ± files ± directories ± file systems
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This note was uploaded on 07/30/2011 for the course COP 4600 taught by Professor Montagne during the Spring '08 term at University of Central Florida.

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Lecture8 - COP 4600 Operating Systems Fall 2010 Click to...

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