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.

21 questions with no upvoted or accepted answers
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When there's no memory, should malloc or read/write fail?

To my surprise, I recently found out that Windows would fail a large memory allocation even if little of said memory is to actually be used, e.g. even if you don't want the swap, you better not ...
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268 views

Paging: Does the page table of a process also gets swapped out when the process gets swapped out from main memory?

Does a process's page table too gets swapped out to secondary storage from main memory when the process gets swapped out to secondary storage from main memory? And gets swapped back in when the ...
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112 views

Isn't resident set management superfluous?

My question is in the context of a paging virtual memory system. THE PREMISES: The function of resident set management (RSM) is to: Impose an upper bound on the cardinality of a process' resident ...
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628 views

How are LRU and Clock algorithm different?

I am modeling the Gclock-pro buffer replacement algorithm in Linux kernel. Because there are many existing modeling works on LRU, I am considering adopting LRU model to roughly describe Gclock-pro, ...
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1answer
1k views

Maximum amount of memory that can be allocated to a process

DISCLAIMER: The following scenario was taken from an assignment I got in a OS course I'm taking, and it arose a lot of question marks in my head. However non of the questions asked by myself here ...
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215 views

pool of free page frames OS

I read that in a paging scheme memory management, some os's have a paging daemon that wakes up periodically to inspect the memory of the RAM. This is to ensure that modified pages can be scheduled to ...
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1answer
2k views

Does Second chance Page replacement algorithm suffer with Belady's anomaly?

In Second chance Page replacement algorithm(clock algorithm), if all the Reference bits are set to one, then the algorithm behaves just as FIFO. Considering this case, can we conclude that Second ...
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8 views

Study of cache behaviour of algorithms on Virtualbox

I want to study certain cache oblivious algorithms and cache behaviour of some other algorithms I wrote in general. I want to understand, is it advisable, if I do this study in an virtualized ...
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15 views

How does increase in main memory affects cache performance?

I know advantages of increase in main memory like more pages , better Spatial locality of reference , more number of processes in main memory and increase in CPU performance. What can be disadvantages ...
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12 views

What happen if the L1 cache has the address entry with write_back attribute. Will that address be available in L2 cache?

I have the TLB entry for a particular address. This address has write-back attributes in both L1 cache and L2 cache. My queries are: 1> if L1 cache entry has write-back, can it be write-back in L2? 2> ...
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23 views

Map a 16Bits to 32 bits address

So, I'm working on a 16 bits CPU Emulator with these settings: Instructions are 4 Bytes long; 24 bits of an instruction are for data purposes, but only 16 bits are used for memory addressing. All ...
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23 views

Calculate the size of memory protection register

One of the methods for virtual memory protection is using a register of accessible pages for every active process. How many bits should the length of this register be, considering: physical memory ...
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268 views

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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53 views

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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52 views

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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68 views

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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51 views

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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458 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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213 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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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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6k views

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 ...