易安信笔试题和面试题答案(二)
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