易安信笔试题和面试题答案(二)

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  13 There is a huge relation R(A,B,C) of size M and A is the primary key. The tuples in R are sorted by using A and no index is built for R. Each disk block size of b, and each block read takes N seconds. To find a tuple in R with A =17954 the estimated optimized cost is

  A M*N/b

  B N*log(M/b)

  C M*N/(2b)

  D (M+N)/b

  E log(M*N)/b

  14 Which of the following descriptions of reader/writer locks are/is wrong?

  A caller cannot upgrade its read lock(already obtained) to write lock

  B caller can downgrade its write lock(already obtained) to read lock

  C caller can get read lock if there is no write lock held by others

  D multiple callers can hold a read lock at the same time

  E only one caller can hold a write lock at a time

  15 两页的内存,四页的文件,读取顺序为 1 2 1 3 1 2 4 2 1 3 1 2 4 2 1 2 3 4 3 1,FIFO,问cache hit ratio为多少

  16 线程

  选项 contained with a process

  share an address space

  share signals

  share errno

  swith的速度比process快

  17 which one is not above IP

  DNS, SNMP, HTTP, ARP, NTP

  18 Map-Reduce Framework

  19 Buffer overflow

  20 system virtualization

  VM, VMM, IO, memory space

  21

  #include

  using namespace

  void main()

  {

  cout << “hello world” << endl;

  }

  修改程序,不能修改主程序,使其输出为

  initiate

  hello world

  destroy

  22 process & thread

  virtual memory space

  kernel register, stack

  fork

  copy-on-write

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