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Definition
| The amount of memory available |
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| A process's view of its own memory. |
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| trying to minimize head movement by organizing how the requests are queued. |
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| type of disk head scheduling, moves to the closest requested track from the current head position. |
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| type of disk head scheduling. Moves the head in one direction until all requests have been serviced in that direction, then reverse the direction. |
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| type of disk head scheduling. It moves the head in one direction until an edge of the disk is reached then reset to the opposite edge. |
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| type of disk head scheduling. moves the head in one direction until no more requests exist between the current head position and the approaching edge of the disk, then the disk head is reset. |
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Definition
| refers to the logical(or virtual) view of how a process is stored in memory. |
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Definition
| the address space supported by the hardware |
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| The address in virtual memory where data/instruction is located |
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| the address in physical memory where data/instruction is actually located in hardware. |
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Definition
| combines assembly code with the code necessary for all code to work (library routines). The address on references change due to the addition of the library routines. |
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Definition
| moving linked code/data into physical memory, where references are translated into their physical values. |
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Definition
| moving something in memory to another place in memory |
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Term
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Definition
| process is moved to another part of memory, but it doesn't require the program to be edited since it keeps logical address rather than virtual or physical address |
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Term
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Definition
| the lowest register in the memory allocated to the next frame. |
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Term
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Definition
| the register that determines the size of the physical address space for a process. |
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Term
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Definition
| unused memory between units of allocation |
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Term
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Definition
| unused memory within a unit of allocation |
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Definition
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Term
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Definition
| place the program in the first space in memory where it fits |
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Definition
| program is placed in the hole closest in size to the program |
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Term
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Definition
| place the program in the biggest hole possible |
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Term
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Definition
| relocate programs to coalesce holes |
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Term
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Definition
| swapping refers to the removal of an entire process from memory when contention for memory becomes too high. It is a form of medium-term scheduling |
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Term
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Definition
| load pages into memory only when a page fault occurs |
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Term
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Definition
| replace a page of the faulting process |
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Term
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Definition
| possibly replace the page of another process |
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Term
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Definition
| the list of pages referenced as time goes by |
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Term
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Definition
| replace the page that hasn't been referenced for the longest time |
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Term
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Definition
| maintains a circular list of pages resident in memory, uses a used bit to track how often a page is accessed. The bit is set whenever a page is referenced. Replace pages that haven't been referenced for once complete revolution |
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Term
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Definition
| modify the clock algorithm to allow dirty pages to always survive one sweep of the clock hand. The dirty bit is when a page is written to. |
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Term
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Definition
| states that more memory does not necessarily lead to better performance. |
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Term
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Definition
| states that 90% of the execution of a program is sequential. Most iterative constructs consist of a relatively small number of instructions. When processing large data structures, the dominant cost is sequential processing on individual structure elements. |
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Term
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Definition
| the number of pages in memory needed to make progress |
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Term
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Definition
| the number of references that can be made before a certain page is replaces if not referenced. |
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Term
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Definition
| replace a page that is not referenced in the next x accesses. |
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Term
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Definition
| if the time between page faults is big, decrease the working set; if the time between page faults is small, increase the working set |
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Term
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Definition
| number of processes in the ready queue |
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Term
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Definition
| Memory is fully allocated. There is a chain of page faults, creates a queue of processes at the paging device. CPU goes close to 0. |
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Term
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Definition
| the individual circle in the disk |
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Term
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Definition
| a sector in software; a space in a disk |
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Definition
| a space on a disk platter |
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Definition
| a certain circumference a head will go through in a disk platter |
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Definition
| the same track on multiple platters |
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Term
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Definition
| on each side of the platters, they read and write data on to them |
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Term
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Definition
| the time it takes for the heads to be moved to the appropriate track |
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Term
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Definition
| wait for the sector to appear under the head |
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Term
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Definition
| read/write the sector to/from main memory |
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Term
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Definition
| array elements map to contiguous sectors on disk. |
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Term
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Definition
| files stored as a linked list of blocks. Directory entry is a pointer to the first and last file blocks |
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Term
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Definition
| create a non-data block for each file called the index block. It has a list of pointers to file blocks. Directory entry is a pointer to the index block. |
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Term
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Definition
| a block(s) on disk containing data storing names, locations, lengths, owner, etc. of all files on disk. Data structures storing free block list. It is stored at a fixed location on disk. It has to search, create, delete, list, and backup files. |
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Term
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Definition
| hides all physical aspects of memory from users, makes memory logically unbounded. |
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Term
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Definition
| physical memory is split up to equal sections, each section is called a page frame |
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Term
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Definition
| a page frame in virtual memory. Same size as the physical page frame. |
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Term
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Definition
| maps virtual pages to physical frames |
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Term
| Translation lookaside buffer |
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Definition
| a cache containing a ordered pairs, matches a page to its corresponding page frame |
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Term
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Definition
| a reference to a non-mapped page |
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Term
| effective memory access time |
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Definition
| = (memory access time*probability of a page hit)+(page fault service time * probability of a page fault). |
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Term
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Definition
| once the size is set in the memory partitions, it stays that way |
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Term
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Definition
| allow the OS change the size of the partitions in memory |
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Term
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Definition
| determining where is the best place in memory to place a program |
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Term
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Definition
| determining which program in memory to take out, in order to replace it with the next program |
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Term
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Definition
-determining how many jobs can be in memory at one time
-determining how much of a job (how many pages of a job) can be in memory at one time |
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Term
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Definition
| memory-management scheme that permits the physical address space of a process to be noncontiguous |
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Term
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Definition
| add additional levels of indirection to the page table by sub-diving the page number into k parts, thus creating a hiearchy of page table. |
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Term
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Definition
| a hash table of virtual memory, matching a process's PID and page number to determine its frame number |
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Term
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Definition
| takes the page table and splits it up into a smaller page table, with each register in it pointing to another page table |
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Term
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Definition
| is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies |
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Term
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Definition
| takes the demands for data and operates the disk-drive hardware to carry out the commands |
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Term
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Definition
| records all the free, usable disk blocks. |
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Term
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Definition
| a collection of a relatively small number of cylinders. File allocation is done within a single cylinder group whenever possible |
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Term
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Definition
| separating the disk into different sections, so it appears to actually be multiple disks. Sometimes the OS doesn't have enough bits to access all the data in the disk |
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Term
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Definition
| accessing the data directly as the requests for it come in |
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Term
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Definition
| split the disk into two equal partitions, when data is written to one, its is written on the other, so that data contents of the two partitions are identical |
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Term
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Definition
| blocks are broken into sub blocks that are stored on separate disks. provides for higher disk bandwidth since the disks can transfer data in parallel |
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Term
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Definition
| has a parity disk. Uses block interleaved parity striping. Allows one to recover from the crash of any one disk |
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Term
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Definition
| block-wise striping. uses parity block interleaving. "horizontal" slices though the data. |
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Term
| parity block interleaving |
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Definition
| the parity block changes disk every time the block is complete. |
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Term
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Definition
| replacing a process's completed part of code in memory with the next part of its code it needs to run |
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