Questions tagged [virtual-memory]

Questions about techniques for providing the appearance of an isolated, contiguous address space to each process. The size of the address spaces may be made to appear larger than the size of main memory by moving pages or segments between main memory and a larger backing store.

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What is difference between parallel virtual machine (PVM) and (mpi) Message passing Interface? [duplicate]

I am using beowulf cluster. And want to know the difference between parallel virtual machine(pvm) and message passing interface(mpi). Thank you.
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45 views

address spaces of changing processes

I read that the mapping for user-space processes is changed after each process switch. By mapping I mean the translation from virtual addresses to "real" memory address. I thought that processes are ...
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Effective Instruction Execution Time with TLB and page Fault

Consider a system with a two-level paging scheme in which a regular memory access takes 150 nanoseconds, and servicing a page fault takes 8 milliseconds. An average instruction takes 100 nanoseconds ...
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Working out logical address space

If I have 2^32 bytes (512 MB) of physical memory, and we assume that each page is 2^10 bytes, how would I work out what the physical and logical address space would be? No explanation that I can find ...
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TLB failure in a memory access

I have come across a question which says If there is a TLB failure in a memory access, the disk must be accessed to load a new page into main memory. The answer is NO, but i dont understand why. Is ...
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468 views

Virtual Memory - Non-contiguous Memory Allocation

I'm studying for my operating systems final, and one question that my professor asked that I can't seem to find the answer to is the following: "Why does virtual memory use non-contiguous memory ...
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What happens when accessing 0x00ABBA?

Given the following page table with a 24 Bit virtual address and 4KB page size and 4 byte long entries (%X means hexadecimal values): I don't understand how to translate e.g. address %X00ABBA here. I ...
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Can the cache always miss while trying to write to the cache?

According to the lecture, a virtual address first goes to the TLB. If the TLB hits, it is then checked, if something has to be either read or written from cache. In case of writing, it is then ...
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85 views

Difference between word logical addressing and byte logical addressing in this exercise?

I´m new here and this is the first question I´m posting (hopefully this is the correct site). I have the exercise below: Consider a virtual address space of 10 pages of 1024 words each (1 word = 2 ...
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751 views

Understanding Logical to Physical Addressing

I am trying to understand the concept of logical to physical addressing. I am given 72 physical addresses (0-71) with values A virtual address = 2^(p+w) p = page bits w = word bits I know the page ...
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463 views

Roles of the Memory Management Unit

I know that the first instruction stored in BIOS is "mapped" to memory address 0, and that a signal on the reset pin to the microprocessor causes this instruction to be fetched, beginning the POST and ...
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216 views

What are current cache algorithms and cache strategies?

Which cache strategies/algorithms (especially for L2 Cache) are used in practice and don't exist solely in research/theory? There is a list on Wikipedia which does not state which algorithms are ...
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Given the logical address, how to extract the page number?

I am studying Computer Systems. I have th following question and its answer: Given the logical address 0xAEF9 (in hexadecimal) with a page size of 256 bytes, what is the page number? Answer: ...
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why do we run out of heap space even if we have virtual memory?

Whenever we try to get space in heap(using malloc or new) we can get out of heap space error if it exceeds the limit. But, we have virtual memory so why can't OS allocate that much space and then do ...
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127 views

In case of program overlays; is it necessary to have error handling routine in memory, regardless of error?

I came accross the question regarding program overlays, ...
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23 views

Why we need tagbits when we already have indexbit and offset?

I was watching a lecture and got confused at one point when professor said that to distinguish between two addresses having same values of offset as well as index bit we need tag.Why we need tag ? for ...
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86 views

What are the differences between embedded processor and non-embedded processor?

I read a statement which says Almost all non-embedded processors, and many embedded processors, support virtual memory Anyone who can explain the difference between both types
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1k views

logical to physical addressing

Consider the page table below (all numbers are in hex) and assume 1 KB page size. Assume 16-bit logical address and 20-bit physical address. a.What are the page numbers and offsets for the following ...
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3k views

How many pages does the page table require?

I have found this exercise on the Internet but I´m having problems with sections 4 and 5, because I don´t understand where do the solutions appear from. Example: Mapping VAs to PAs Suppose - ...
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2k views

How do i find bits in virtual and physical address?

The question is: ...
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2k views

What's the difference between clock replacement & LRU replacement?

As title. When we want to request following page numbers 2,4,4,2,5,2,1,1,3,1, is clock replacement better? What are the advantages and disadvantages of them? Thanks~
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How to calculate page size of virtual memory

im new at OS and I want to know how to calculate the page size of this virtual memory system? Information: Physical Memory - 32 KB Virtual Address - 16 bit Offset - 12 bits Current ...

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