OS General Concepts Interview Questions And Answers. Each. page can be either. In memory (physical page frame). On disk (backing store). Page fetching: when to bring pages into memory.* Page replacement: which pages to throw out of memory.
Page Replacement* Once all of memory is in use, will need to throw outone page each time there is a page fault.* Random: pick any page at random (works surprisingly well!)* FIFO: throw out the page that has been in memory longest.* MIN: The optimal algorithm requires us to predict thefuture.* Least Recently Used (LRU): use the past to predict thefuture.* Strange but true: for some placement policies, such as. FIFO, adding more memory can sometimes cause pagingperformance to get worse. To choose page for placement: o Start with FIFO approach: cycle through pages inorder circularly. If the next page has been referenced, then don'treplace it; just clear the reference bit and continue to thenext page. If the page has not been referenced since thelast time we checked it, then replace that page. If a dirty page isreplaced, it must be written to disk before its page frameis reused.* The clock algorithm typically gives additionalpreference to dirty pages. For example, if the reference butfor a page is clear, but the dirty bit is set, don't replacethis page now, but clear the dirty bit and start writing thepage to disk.* Free page pool: some systems keep a small list ofclean pages that are available immediately for replacement.
During replacement, take the page that has beenin the free pool the longest, then run the replacementalgorithm to add a new page to the free pool. Pages in the free pool have their exists bitoff, so any references to those pages cause a page faulto If a page fault occurs for a page in the freepool, remove it from the free pool and put it back inservice; much faster than reading from disk. Provides an extra opportunity for recovery if wemake a poor page replacement decision.
Usually thrashing refers to two or more processes accessinga shared resource repeatedly such that serious systemperformance degradation occurs because the system isspending a disproportionate amount of time just accessingthe shared resource. Resource access time may generally beconsidered as wasted, since it does not contribute to theadvancement of any process. This is often the case when a. CPU can process more information than can be held inavailable RAM; consequently the system spends more timepreparing to execute instructions than actually executing them.
Operating Systems Interview Questions & Answers: An operating system (OS) is system software that manages computer hardware and software resources and provides common. 30 important-virtualization-vmware-interview-questions-with-answers 1. 30 Important Virtualization-VMware Interview Questions with.
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