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10 Cards in this Set
- Front
- Back
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Page address |
is the same as logical address = page number + page offset
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frame address |
same as physical address and represented by frame number + page offset |
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Page map table |
a data structure used to keep track of the relation between a page of a process to a frame in physical memory |
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MMU - memory management unit |
the hardware required for paging |
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what does the page table base register do? |
points to the page table |
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what does the page table length register do? |
indicates the size of the page table |
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paging hw |
in this scheme, every data/instruction access requires two memory accesses; one for the page table and one for the data/instruction |
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Paging implementation issues |
1. mapping from virtual addresses to physical address must be fast 2. if the virtual address space is large, the page table will be large |
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the solution to having to use 2 memory accesses for paging? |
TLBs- a special fast lookup hardware cache called associative memory or Translation Look-aside Buffers |
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Page fault handling |
1. the hardware traps to the kernel, saving the program counter on the stack 2. an assembly code routine is started to save the general registers and other volatile information 3. the operating system discovers that a page fault has occurred and tries tobdiscover which virtual page is needed 4. once the virtual address that caused the fault is know, the system checks to see if this address is valid and the protection consistent with the access 5. if the pagebframe selected is dirty, the page is scheduled for transfer to the disk, and a context switch takes place 6. when the page frame is clean, OS looks up the disk address where the needed page is, schedules a disk operation to bring it in 7. when disk interrupt indicated page has arrived, page tables updated to reflect position, frame marked as being in normal state 8. faulting instruction backed up to state it had when it began and program counter reset to point to that instruction 9. faulting process scheduled, OS returns to the assembly language routine that called it 10. this routine reloads the registers and other information and returns to user space to continue execution, as if no fault had occurred. |
