Comp111 - Quiz 2 Review 3
Dec 8, 2009 - closed book
Please fill in the blanks. Each blank is worth 5 points.
There are several reasonable answers for some of the blanks; choose one.
Blanks with the same number have the same answer.
Extra credit answers count only if errors are made in the regular quiz;
in no case will one's score be greater than 100.
Each page in a memory page table has attributes known to the operating
system but not necessarily known to the processes that utilize the page.
These attributes include whether the page is
________1________ to a process, as well as whether it
________2________ with other processes.
These attributes take up a significant amount of space in memory,
so that some operating systems define them by specifying them for each
________3________ rather than for each page.
- An inverted page map differs from a regular page map because
each page address is
________4________ into an offset
into the page table rather than being interpreted as an offset into
the page table. This means that one can often hop directly to
the appropriate page map
entry, but sometimes one must
________5________ within the
page table for an appropriate entry.
Each entry of an inverted page map must thus contain the real offset
of the page, as well as an identifier of the
________6________ that owns the page.
Without this extra information, the mapper can't tell the difference between
pages intended for use by different
- The inter-arrival time and service time distributions actually have the same
________8________ distribution function
but describe different things. The
inter-arrival time distribution describes
successive events, while the service time distribution describes time
required to ________10________ a particular event.
If λ represents the rate of arrival of events, and μ represents
the rate of processing, then λ/μ represents the
that the associated queue of events contains 0 elements,
while (λ/μ)n(1-(λ/μ)) represents the
________11________ that the queue contains exactly n elements.
This is only true if the queueing system achieves steady-state behavior, i.e.,
λ/μ < ________12________.
If it achieves steady-state behavior, the balance equations say that
the input and output
for each particular queue are the same, while the
________14________ for each queue may differ greatly from
that of other queues.
- In paging systems, the translation lookaside buffer serves as a
________15________ of the translations between
and physical page addresses.
As it is limited in size, its contents are sometimes treated as
memory, and paged in and out just like process pages.
In assignment three, the deadlock detection algorithm often detects
deadlock conditions that do not persist. This is because the deadlock
is caused by choices made by the
rather than choices made by the processes.
Unlike individual processes, the pager has a
view of resource needs over all processes.
This means that it can
potential deadlock conditions when they occur, simply by making
more informed choices.
- (EXTRA CREDIT: can increase score to 100, but not above 100)
A virtual memory paging system may be modelled as an M/M/c queueing system,
where 1/λ is the average time between page
1/μ represents the average time it takes to
________22________ a page into physical memory, and
c represents the number of
________22________ operations that can occur concurrently.
Increasing the amount of physical memory
________23________ λ; this is strongly recommended