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Now, let us discuss two related algorithms for deciding which pages to evict. The clock algorithm is one of the most popular choices. It works by keeping frames in a circular structure. (Note that this circle may be very large: a 32-bit machine with 4k pages can have up to 220 1 million frames.) When a page fault occurs, it checks the reference bit of the next frame. If that bit is zero, it evicts that page and sets its bit to 1; if the reference bit is 1, the algorithm sets the bit to 0 and advances the pointer to next frame.
An implementation which is often used in real operating systems is a segmented queue. This type of algorithm divides all existing pages into two sets of pages. The most-active one-third of all pages use a clock algorithm. After that, pages that are evicted out of the clock are moved to a "uncommon" linked list, in which we use exact LRU. This way, we approximate LRU for the frequently-referenced pages (1/3 of the page frames - fast clock algorithm), and at the same time use exact LRU on the infrequently accessed pages (2/3 of all page frames). Since the pages in the uncommon list are not accessed very frequently, it is okay if their accesses are a little slower due to some pointer manipulation.
Partitions and mounting A disk can be sliced into many partitions, or a partition can span multiple disks. Every partition can be either "raw", having no file system, or "cooke
Define the “turn-around” time of a user job Turn- around time is total time taken to execute the job.
about error detection in operating system and how does it take place?
Second-Chance algorithm When a page has been selected, we inspect its reference bit. If the value is 0, we proceed to replace this page. If the reference bit is set to 1, thoug
why we say " OS is a resource allocator" and “OS is a control program"?
Thermostats are subjected to rigorous testing before they are shipped to air conditioning technicians around the world. Results from the last five samples are shown in the table. D
What is meant by arm-stickiness? If one or a few processes have a high access rate to data on single track of a storage disk, then they might be monopolizing the device by repe
Q. What is Multiprogramming? Multiprogramming When two or more programs are in memory at the same instance, sharing the processor is referred to multiprogramming opera
properies of Batch oriented and interactive operating system.
Acyclic-graph directories An acyclic graph permits directories to have shared subdirectories and files. The similar file or subdirectory may be in two dissimilar directories. A
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