Comp111 - Operating Systems

Quiz 2 - Dec 3, 2014 - closed book



Closed book and notes. No electronic devices allowed. Please fill in the blanks. Each blank is worth 5 points. Blanks with the same number have the same answer.

  1. Little's laws are based upon the assumption that the system is in ____balance/equilibrium____ so that the ____input____ and output of the system occur at the same ____average____ rate. If λ is an arrival rate, then ____1/λ____ represents the corresponding time between arrivals. M/M/1 queues assume in addition that arrivals and processing have ____exponential/memoryless____ statistical distributions.
  2. The ____O(1)____ scheduler for linux minimizes computation at the expense of non-optimal ____fairness____. The main feature of this scheduler is that every process in the run queue gets a constant amount of runtime per ____epoch/slice____.
  3. In an operating system, ____internal____ fragmentation refers to unused space in the memory space of the requesting process, while ____external____ fragmentation refers to unused space outside the requesting process in the operating system.
  4. In a file system, a(n) ____inode____ documents the location of a file, while a(n) ____directory____ documents its name. In order to create a file one must initialize these and also mark the disk space required as ____used____. This is typically done through the use of ____bit/binary____ vectors.
  5. The buddy system guarantees that if one frees and then reallocates the same amount of storage, one will always get the ____same____ memory back when asking again. This is because the freed block is linked at the ____head____ of the appropriate free list.
  6. The fact that multiple processes share the same kernel descriptor for the same file means that output from the processes is appended to the file in ____time order/sequence____. If multiple processes write to independent kernel descriptors, then the content of the file is determined by the ____last/latest____ process to close it.
  7. The I/O subsystem is a concatenation of multiple producer-consumer systems. For example. in writing to the raw disk, the producer is ____running processes____, while the consumer is the ____disk scheduler/update____.
  8. (Extra credit) The Ext2 filesystem and its derivatives only function properly because of the ____paging_____ subsystem for the raw disk device.