Comp111 - Quiz 2

Dec 9, 2015 - closed book



Please fill in the blanks. Each blank is worth 5 points. There are several reasonable answers for some of the blanks; choose one. Blanks with the same number have the same answer.

  1. The structure of a linux filesystem is based upon a contractual arrangement between the ________1________ and the ________2________. The former determines the structure of disk, while the latter makes disk updates ________3________.
  2. The ________4________ reclamation strategy is commonly used to recover pages in the disk page table. This has one weakness; it does not deal efficiently with ________5________.
  3. Little's law relates arrival rate, time in system, and ________6________ for a queueing process. Little's law only requires that the system be ________7________. This is in contrast to all further results in queueing, which require some kind of assumption about the ________8________ of arrival times and/or service times.
  4. An M/M/1 queue is a device where job arrivals and service times conform to ________9________ statistical distributions. Since real service times are not ________9________, the theory of M/M/1 queues rather consistently ________10________ the average time in system for a request.
  5. Every file in a linux filesystem is described by an ________11________ that describes the owner, group, protection, and location of blocks in the file. The location of the first few blocks of the file are recorded directly inside the inode, while subsequent blocks are located by ________12________ in which a block is re-interpreted as an array of ________13________ to blocks. Thus a file is logically a list but physically very similar to a(n) ________14________, in the sense that access to any block is O(1).
  6. In assignment four, getting the very best score is extremely difficult, because seemingly small errors in code do not lead to crashes, but instead decrease ________15________.
  7. Long term scheduling, also called ________16_________ control, determines when a job should ________17________ rather than when it should continue.
  8. The completely fair scheduler attempts to give each process in the run queue the ________18________ time per scheduling epoch, while in the O(1) scheduler, processes get differing times based upon how much ________19________ they perform.
  9. The "systems monoculture" refers to the fact that several commonly available operating systems encourage all instances to have the same ________20________ which means that any attack that compromises one of them compromises all of them.
  10. (EXTRA CREDIT ) In allocating a new block for a file, the filesystem driver first looks for blocks whose "used" descriptors are currently located in the ________21________, to increase performance.