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+2 votes

Which of the following are the likely causes of thrashing?

  1. Page size was very small.
  2. There are too many users connected to the system.
  3. Least recently used policy is used for page replacement.
  4. First in First out policy is used for page replacement.
in Operating System by Boss (30.9k points) | 3.4k views
all options could be a reason for thrashing to some extent but the most appropriate and effective from given options is A.

6 Answers

+7 votes
Best answer

Answer is A

With a computer, thrashing or disk thrashing describes a condition when a page is moved to hard sick from main memory inorder to bring in another page and the moved out page has to come to main memory again which causes another important page to be swapped out and this causes a chain of page swaps and thus slowing down the system enormously. Thrashing occurs when the system does not have enough memory, the system swap file is not properly configured, too much is running at the same time, or has low system resources.

Even if users are more we cannot say it can directly cause thrashing as they need not be using a lot of memory. (Increasing the level of multitasking is a possible cause of thrashing as it causes more no. of processes to require pages in memory simultaneously)

A is a better answer here because if page size is large there will be lesser number page swaps -- say if page size is 4KB, and there are 100 page swaps, if page size is made 8KB, we expect the number of page swaps to be reduced to 50 (this can be any value from 0-100, but expected value is 50).

by Active (3.9k points)
selected by
+4 votes

if page size is very small , locality of reference will be reduced. which increases page faults.

by Active (3.5k points)
+2 votes
B) There are too many users connected to the system.
by Veteran (119k points)
+1 vote

thrashing is due to page fault . if required page not in main memory i.e one can be frame are not able to hold all pages needed

size of frames = size of pages so if page size is small it will result in many frames and pages so chances less of page fault but we can't conclude from that just .

and we know FIFO suffer belady's anomal FIFO as even on incresing frame size or page size for few refrences it will suffer thrashing always

but i feel  it is B as for some references fifo would be good for some page size

but if increse user many process may be in one cpu so many page refernces  might  causing page faults

by Junior (777 points)
+1 vote
Thrashing is a condition  when  excessive paging are taken place .

For Option a : If they say page size is too small , Then for a process running It can bring more number of pages in memory . SO you dont have excessive paging . You have majority of pages in memory

For optio D and C : FIFO and LRU cant solve Thrashing problem . I think priority based algorithm can solve this problem . Hence it is wrong

For option b : There are many user connect to the system . mean many process are simultaneously running in the system.

For more process less number of pages for each process would be in memory . So now for majority of new page request by a process it has to replace its exists page . Hence the process of paging is done every now and then .

So b is answer
by Loyal (9.9k points)
0 votes

ans is (a)

Thrashing is a state in which the CPU performs 'productive' work less, and 'swapping' more. The CPU is busy in swapping pages so much that it can not respond to users' programs and interrupts as much as required. Thrashing occurs when there are too many pages in memory, and each page refers to another page

by Active (4.9k points)

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