Comp111 - Operating Systems

Quiz 2 - Dec 8, 2009 - closed book

Name:________

Login:______________

Please fill in the blanks. Each blank is worth 5 points. Blanks with the same number have the same answer.

  1. A device driver is nothing more than a set of ____functions____ that describe how to ____interact____ with a device. Each device has a "major number" that serves as an ____index/offset____ into a table of drivers.
  2. The disk subsystem and the virtual memory subsystem both use the concept of ____paging____ things to and from memory, but the disk subsystem uses ____kernel____ memory while the virtual memory subsystem utilizes ____process____ memory.
  3. Little's law says that the "average jobs in system" = ____(average) (job) arrival rate____ times the "average job time in system". It requires only that the input and output rates be ____balanced/the same____ and does not depend upon any statistical properties of processing or job arrival.
  4. A memory page that has been changed since it was read from disk virtual memory is called ____dirty____ and must be ____flushed/written____ to the disk before the memory can be reused.
  5. Likewise, a block of memory representing a disk block that has changed since it was read from the disk is called ____dirty____ and must be ____flushed/written____ to the disk before the memory can be reused.
  6. An M/M/1 queue with arrival rate λ and processing rate μ is only in steady state if ____λ/μ____ < 1. Both 'M's in the above stand for ____memoryless____, which means that a previous arrival time or processing time does not affect the next.
  7. A(n) ____segment____ of memory is a region of memory that shares the same protection settings, while a(n) ____page____ of memory is the smallest amount that can be allocated to a process. A typical memory addressing scheme includes bit fields that represent both of these, as well as the ____offset/address____ of the byte or word we want. Because memory maps for processes are sparse, ____hash tables/hashing____ is often used to locate memory from its address.
  8. A disk file is identified via a(n) ____inode/identity node____ that describes access privileges and where its contents are, but does not contain its ____name____, which is instead contained in the directory in which the file resides.
  9. The geometry of a modern disk -- described in terms of cylinders, tracks, and sectors -- is a(n) ____falsification/illusion/fabrication____. The raw disk is a(n) ____block____ device, and can only read or write a whole one at a time.