lecture25-chapter11 - OperatingSystems Lecture25:...

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Operating Systems Lecture 25: I/O Management Anda Iamnitchi anda@cse.usf.edu 1
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Roadmap I/O Devices 11.1 Organization of the I/O Function Operating System Design Issues I/O Buffering Disk Scheduling Raid Disk Cache 2
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I/O Device Data Rate May be massive difference between the data transfer rates of devices 3
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A Typical Hardware System main memory I/O bridge bus interface ALU register file CPU chip system bus memory bus disk controller graphics adapter USB controller mouse keyboard monitor disk I/O bus Expansion slots for other devices such as network adapters. 4
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Reading a Disk Sector: Step 1 main memory ALU register file CPU chip disk controller graphics adapter USB controller mouse keyboard monitor disk I/O bus bus interface CPU initiates a disk read by writing a command, logical block number, and destination memory address to a port (address) associated with disk controller. 5
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Reading a Disk Sector: Step 2 main memory ALU register file CPU chip disk controller graphics adapter USB controller mouse keyboard monitor disk I/O bus bus interface Disk controller reads the sector and performs a direct memory access (DMA) transfer into main memory. 6
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Reading a Disk Sector: Step 3 main memory ALU register file CPU chip disk controller graphics adapter USB controller mouse keyboard monitor disk I/O bus bus interface When the DMA transfer completes, the disk controller notifies the CPU with an interrupt (i.e., asserts a special “interrupt” pin on the CPU) 7
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Disk Geometry Disks consist of platters , each with two surfaces . Each surface consists of concentric rings called tracks . Each track consists of sectors separated by gaps . spindle surface tracks track k sectors gaps 8
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Platter View) Aligned tracks form a cylinder.
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lecture25-chapter11 - OperatingSystems Lecture25:...

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