Term
| logical address vs physical address |
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Definition
Logical address generated by CPU
address seen by the memory unit—that is, the one loaded into the memory-address register of the memory-- is commonly referred to as a physical address |
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Term
| Contiguous memory allocation vs. paging |
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Definition
-contiguous memory allocation, each process is contained in a single contiguous section of memory
-contiguous memory allocation suffers from external fragmentation,
-contiguous memory allocation uses base and limit register for mapping
-paging does not suffer from external fragmentation
-paging (accesses memory twice)
-paging allows the physical address space of a process to be noncontiguous, physical address space of process is scattered throughout memory
-paging avoids the considerable problem of fitting memory chunks of varying sizes onto the backing store |
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Term
| External fragmentation VS internal fragmentation |
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Definition
-external fragmentation – as processes are loaded and removed from memory the free memory space is broken in to little pieces.
- 50 percent rule - as much as one-third of memory may be unusable because of external fragmentation
-internal fragmentation – more memory is allocated to a process than what the process originally requested |
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Term
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Definition
| holds the smallest legal physical memory address |
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Term
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Definition
| specifies the size of the range |
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Term
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Definition
| the set of all logical addresses generated by a program |
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Term
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Definition
| the set of all physical addresses corresponding to these logical addresses |
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Term
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Definition
| handles all mapping from virtual to physical addresses |
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Term
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Definition
| one solution the external fragmentation The goal is to shuffle memory around as to place all free memory togethor |
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Term
| transient operating-system code |
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Definition
| size of operating system changes in memory to allow space for user land programs |
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Term
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Definition
| simplest method for allocating memory is to divide memory into several fixed-sized partitions. |
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Term
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Definition
| chunk of memory available for user program |
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Term
| dynamic storage-allocation problem |
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Definition
| concerns how to satisfy a request of size n from a list of free holes |
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Term
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Definition
| allocate the first hole that is big enough |
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Term
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Definition
| allocate the smallest hole that is big enough |
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Term
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Definition
| allocate the largest hole |
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