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| title | aliases | tags | ||
|---|---|---|---|---|
| 21-memory-management |
|
storage heirachy
primary storage - cache and main memory
secondaryy - hard drive
as we move from secondary to primary:
- access speed increases
- access time decreases
- cost increases
- capacity decreases
process memory image and logical and physical addresses
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a program is compiled and linked into a process image before loading into memory for execution
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a process memory image consists of code section, data sections, lib sections, and stack sections
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each process has its own logical memory space starting from 0 and ending at a maximum address
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the logical address has to be translated into physical address before sending the memory request to the physical memory modules
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the memory management unit (MMU) translated between the logical addresse and the physical addresses.
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physical mode - progam refers directly to physical address
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protected mode - dont allow program to use physical address directly - uses logical address
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OS kernel creates a map from logical address to the physical address using a mapping table
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CPUrefers to this table to map between physical and logical address
paging for memory translation
Noncontiguous paging: a processes logica address pace is broken int fixed size units called pages, and main memory is broken into units of the same size, called frames.
in a paged memory allocation scheme, the logical sddresses generated by the CPU are broken by special ardware itno two components:
- page number
- offset (address within page)
