[問題] OS-一些問題...
問題有點多...
1.
Suppose the linux scheduler choose the process with the most credits to
run, and if no runnable processes can be chosen , the recrediting
operating is pf=erformed according to the following rule for every process
in the system: credits = credits/2 + priority
for each time slice, currently running process will lose one credit.
When the credits reach zero, itis suspended. According to the above
description, which of the following statements is correct?
a)this credit system gives high priority to cpu-bound process
b)the scheduling will exhibit short response time
c)interactive processes will receive fewer eredits than non-i/o bound
process
d)none of the above
2.
In operating systems the scheduler performs a rescheduling when current
process request an I/O, the time slice assignedto current process is
exhausted, the current process yields, or higher-priority process
arrive. One every rescheduling , it will take time for the kernel to
perform context switch.It it possible for a round-robin scheduler with a
100 millisecond time slices to spend over half its time in the OS context
switch code? Assume that it take the OS 1 millisecond to context switch the
CPU. Please justify your answer and give an example.
3.
consider a system with three resource types with the vector Avalable
initialized to (7,2,6).Suppose at time T0, process A has the resource
vector of (0,1,2),process B has the resource vector of (2,0,0),and
process C has the resource vector of (3,0,3). If process A requests for
extra resource vector of (3,0,0), it is blocked since not enough resource
available for allocation. Which necessary condition cannot occur for not
enough resource available for allocation. Which necessary condition cannot
occur for not entering deadlock state?
a)process B asks for extra(0,1,1) and process C asks for extra (4,0,0)
b)process B asks for extra(0,1,1) and process C asks for extra (0,0,1)
c)process B asks for extra(4,1,2) and process C asks for extra (0,0,1)
d)process B asks for extra(5,2,5) and process C asks for extra (2,1,0)
e)none of the above
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