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Questions tagged [paging]

Questions about memory-management techniques where the computer manages and transfers data between main memory and secondary storage in pages -- discrete chunks of a fixed size. Operating systems often use paging to implement virtual memory.

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2answers
374 views

Are there any garbage collectors that take into account paging?

Garbage collections have to visit all objects that are alive, so as to find the memory that can be reclaimed. (Having many generations’ just delays this a bit) All things being equal, it is ...
11
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1answer
4k views

Swap space management during pure demand paging

The following is a doubt that I came across while doing a OS home assignment - however, it seems more concept-based than a straightforward coding question, so IMHO I don't think the homework tag is ...
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2answers
7k views

Can someone explain this diagram about Slab Allocation?

I'm trying to understand how Slab Allocation works and why it is different or better than ordinary paging. I found this diagram which I believe would be helpful if it had more explanation. Some ...
9
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2answers
32k views

Clock page replacement algorithm - Already existing pages

When simulating the clock page replacement algorithm, when a reference comes in which is already in memory, does the clock hand still increment? Here is an example: With 4 slots, using the clock ...
7
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2answers
13k views

Is page size always equal to frame size?

I'm learning about paging. My book says that the logical addresses generated by the CPU are in the form |p|d|(page number, page offset) and the physical addresses ...
6
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2answers
27k views

How does increasing the page size affect the number of page faults?

If we let the physical memory size remain constant, What effect does the size of the page have on the number of frames? What effect does the number of frames have on the number of page faults? Also,...
6
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1answer
2k views

How to interpret “Windows - Virtual Memory minimum too low” from a CS student point of view?

On my old 256MB RAM, pc I get this message. (I guess it is quite common) Windows - Virtual Memory minimum too low Your system is low on virtual memory. Windows is increasing the size of your ...
5
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3answers
5k views

Look Ahead buffer vs Translation Look aside buffer

I know that Translation look aside buffer is used for address translation in paging to achieve better performance. I came across term called Look Ahead buffer in a document which said it implements ...
4
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1answer
3k views

What is the difference between LRU implemented for a cache and for page replacement?

I have read that true LRU page replacement requires significant hardware support, so only approximation of LRU is implemented for page replacement. So I wanted to contrast LRU that is implemented for ...
3
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3answers
3k views

Virtual Address and Physical Address Space

A machine has 48-bit virtual addresses and 32-bit physical addresses. Pages are 8K. How many entries are needed for a conventional page table ? The answer is 2^35 entries Why not (2^32) / (2^13) = ...
3
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2answers
2k views

How to calculate the size of a page in a two level paging CPU?

I am having difficulties with understanding the concept of paging. As a result I've got no idea how I can solve the following exercise - I'm lacking one more equation to solve it. I've read a lot ...
3
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1answer
3k views

Page Table Size in a 4 Level Hierarchical Page Table

An Intel 64 bit CPU uses a four-level hierarchical page table. Each of the four levels of the page table can contain 512 entries, and the page table size is 4KB. You should be able to see that it ...
3
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1answer
274 views

Best design of a software controlled page table: to echo the TLB?

I am building some simple system software for the Microblaze FPGA (actually being run on OVPsim at least for now). The system is to experiment with various memory management regimes. The first ...
3
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0answers
197 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 ...
2
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4answers
7k views

Why do we need the valid-invalid bit in a page table?

I'm reading about memory management in Operating System Concepts, by A. Silberschatz. The author says: [...] the user process by definition is unable to access memory it does not own. It has no ...
2
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1answer
10k views

Hierarchical Paging

Suppose I have a system with 32-bit logical and 16-bit physical address spaces, and the page size is 512 bytes. For simplicity, ignore the valid/invalid bits in the page table. How many sections will ...
2
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4answers
8k views

Calculation of effective average instruction execution time in a 2-level paging system

System has a two level paging scheme Average CPU time for a instruction = 100ns Average number of memory accesses per instruction = 2 Regular memory access = 150 ns Page fault service time = ...
2
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1answer
340 views

Practical Page-Replacement Algorithms

Could anyone suggest other page replacement algorithms that are applicable to the real world aside from FIFO, Second Chance (Clock), Enhanced Second Chance and Random?
2
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1answer
679 views

Operating system maintains copy of page table for each process

I am quoting a paragraph in Operating System Concepts by Silberschatz, in paging chapter, In addition, the operating system must be aware that user processes operate in user space, and all ...
2
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1answer
8k views

What's the difference between Clock and Second Chance Page-Replacement Algorithm?

I know that they both have reference bit, but I only understand the Second Chance but not the Clock Page-Replacement algorithm. could anyone help me understand?
2
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1answer
32 views

What does it mean " The outer level page table need not be page aligned?

The question is in context to multilevel page table. I was trying to solve numerical on multi-level paging and noticed that page size might not be same at all levels. I came across the point "Outer ...
2
votes
1answer
200 views

How does hashed inverted page table work?

I understand hash function and inverted page table, but then the book I read describes something called hashed inverted page table (use hash to accelerate the finding because IPT is large), with TLB ...
2
votes
1answer
1k views

Second Chance Page Replacement

In the second chance page replacement algorithm, if a page's reference bit is already set to 1, and the next page in line of the reference string is the same page, does the reference bit stay at 1 or ...
2
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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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2answers
47 views

What is the difference between a page and thread?

"Each process that is executed is divided into blocks of same size, called pages." "Thread is a part of process being executed." Are pages and threads both part(s) of process? Whats the difference ...
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1answer
2k views

What are logical addresses and where do they actually reside?

While studying about memory management, paging and segmentation there is a lot of usage of phrases like CPU generates logical addresses and ...
1
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1answer
812 views

Processes and Segmentation

The following problem was on my final and in Gate 2006, but I don't understand how to solve it: Different methods of memory management have different overheads: ...
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2answers
41 views

If you increase the address space for an OS, does the Phys Mem used by the program increase?

I am learning about the OS. I know: that Address Space Size = # of pages x page size So if I increase Address Space Size, then the number of pages increases:(not the page size). However, isn't the ...
1
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1answer
10k views

How to calculate virtual address space from page size, virtual address size and page table entry size?

I try to solve an exercise, unfortunately without any success yet. From the following given information, the virtual address space should be calculated: Page size is 16 KB Logical address size is 47 ...
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2answers
184 views

Does the Working Set Paging Algorithm use a separate page table?

I am doing research on paging algorithms. While learning about the working set algorithm from several scientific sources I was not really able to figure out where exactly the working set is defined or ...
1
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2answers
734 views

Question on Virtual memory and Physical memory

This is the question where I'm stuck: With a 32-bit virtual address, 4 KB pages(12 offset bits), and 4 bytes per page table entry, we can compute the total page table size: Number of page table ...
1
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1answer
326 views

In an Inverted Page Table, will following chains happen very often for small addresses?

I just learned about the Inverted Page Table and immediately thought about the chaining model used. If two processes use the same virtual address, resolving the address will have to include following ...
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1answer
1k views

Does virtual address space resides in virtual memory?

I have several confusion like : Does virtual address space resides in virtual memory ? Does each process has its own virtual address space like each process has its own virtual memory and own page ...
1
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1answer
287 views

clarification about Algorithm of page replacement LRU with reference bits

Studying LRU approximation Algorithms I think to have not understand how it works, for example: ...
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1answer
615 views

How to find the virtual pages and physical memory frames?

So i am given a system of 20 bits virtual addresses and 18 bits physical addresses using paging with pages size 4Kbytes. I am told to find the maximum number of virtual pages that a process can have ...
1
vote
1answer
48 views

Is the term page replacement actually a misnomer?

My understanding is that "page replacement" entails replacing the contents of a frame to bring in a new frame in it's place corresponding to a new page. Since it is not the page, but the frame that ...
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0answers
41 views

Difference between present - absent bit and valid - invalid bit in a page table?

while reading I found this: Present/Absent bit – Present or absent bit says whether a particular page you are looking for is present or absent. In case if it is not present, that is called Page ...
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0answers
115 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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0answers
288 views

Difference between inverted page table and a standard one?

I know that for standard page tables each process would have its own page table and for inverted the OS would have it. But other than this what are the main differences between a standard page table ...
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0answers
387 views

Clock variant of the Second-Chance page-replacement Algorithm vs. standard Second-Chance Algorithm

A sample question for my upcoming Operating Systems exam is: Under which circumstances would the clock variant [of the second-chance algorithm] be preferred over the standard second-chance ...
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2answers
201 views

Can this question be solved without knowing the Page Table Entry?

I'm preparing for the exams and this question came up - Consider a machine with $64MB$ physical memory and a $32$-bit virtual address space. If the page size is $4KB$, what is the approximate size ...
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0answers
1k views

want to know concept behing Multilevel paging

In order to use large size page table hierarchical paging is done . In case of two level page table scheme . for : logical address space - 32bit - $2^32$ page size - 4kb i.e $2^12$ It is mentioned ...
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0answers
5k views

Effective Acces time in Demand Paging system with Associative memory

Q: Consider a demand-paging system with a paging disk that has an average access and transfer time of 20 milliseconds. Addresses are translated through a page table in main memory, with an access time ...
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3answers
58k views

How to work out physical address corresponding to logical address?

I am looking to calculate the physical address corresponding to a logical address in a paging memory management scheme. I just want to make sure I am getting the calculation right, as I fear I could ...
1
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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 ...
0
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1answer
407 views

How does cpu fetch active program data (using virtual address) from storage when there is a page fault?

I read that cpu generates virtual address and using the same mmu translates to physical address and then fetches the data from RAM. But when there is a page fault, the data is fetched from the HDD(or ...
0
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2answers
452 views

Why page size = size of one cache way?

Why is that the page size equals the size of one cache way? My book states "A direct-mapped cache cannot be bigger than a page".
0
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1answer
2k views

What is the difference between caching, buffering and paging? Expecting a detailed answer on the OS level

I have been reading about caching and buffering it seems about the same to me can't get hold of the differences clearly and paging, for now the only difference I understand between paging and caching ...
0
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1answer
841 views

Calculating cache memory based on LRU algorithm

Assuming i have 4 blocks of cache memory, Using the LRU (Least Recently Used) replacement algorithm on this following sequence of access to memory blocks: 1 2 3 4 5 2 5 4 1 5 2 3 : ...
0
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1answer
918 views

Segmentation and paging

I am given a system with a segmented paging architecture. Both physical and virtual address spaces contain $2^{16}$ bytes each. The virtual address space is divided in $8$ equal size segments. The ...