Computer Science - Operating Systems Concepts - Discussion

Not all virtual memory systems are prone to thrashing. Thrashing is consequence of paging and not virtual memory.

The VAX-11 ISA that use a Paged Page Table in the virtual memory is the perfect example of Thrashing, not because it uses virtual memory but because it has to fetch the pages of the page table from the virtual memory causing thrashing.

The exact same VAX-11 ISA if used with 256 byte page size (instead of 512 byte) and 8-bit page address (instead of complete 22-bit available) has absolutely no thrashing whatsoever due to the page table being always loaded on the physical memory. It still has a 30-bit address bus for virtual addressing.

Thrashing can be caused by poor paging algorithm is partially correct. The correct answer to the question would be (A).

Thrashing occurs when a system spends more time processing page faults than executing transactions.

A process is thrashing if it is spending more time paging than executing.

Thrashing is a phenomenon in virtual memory schemes when the processor spends most of its time swapping pages, rather than executing instructions. This is due to an inordinate number of page faults.

If the no of process sumbited to the cpu for execution are increased the cpu utilisation will also increases. But increasing the process contineously at certain time the cpu utilisation falls sharply & sometimes it reaches to zero. This situation is said to be "Thrasing".

The effective CPU utilization is only possible if the CPU can execute more pages. but a certain time will came when there will be more demand paging now that means the CPU only do swap but no execution ..at that moment the utilization generally degrades..this period is called trashing period...

Thrashing is a prosses by which we can used the rate of cpu utilization low as campared to origniol we have increase the prossses to inceases the cpu utilization but it give us the max no of page fault thats why it decrease the cpu utization.

Sundar is correct but, Thrashing occurs due to the quick paging in small intervals. So the CPU waste time in paging activity rather doing actual work.

In computer science, thrashing is a situation where large amounts of computer resources are used to do a minimal amount of work, with the system in a continual state of resource contention. Once started, thrashing is typically self-sustaining until something occurs to remove the original situation that led to the initial thrashing behavior.

Usually thrashing refers to two or more processes accessing a shared resource repeatedly such that serious system performance degradation occurs because the system is spending a disproportionate amount of time just accessing the shared resource. Resource access time may generally be considered as wasted, since it does not contribute to the advancement of any process. This is often the case when a CPU can process more information than can be held in available RAM; consequently the system spends more time preparing to execute instructions than actually executing them.

Silly window syndrome is a type of communications system thrashing.