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Operating Systems
final
114
Computer Science
Undergraduate 4
05/15/2012

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Cards

Term
In uniprocessor scheduling, the most important criterion is the CPU utilization efficiency.
Definition
true
Term
First Come First Served policy is biased against short processes.
Definition
true
Term
First Come First Served policy is biased against IO bound processes
Definition
true
Term
Round Robin policy is biased against long processes.
Definition
false
Term
Round Robin policy is biased against short processes
Definition
false
Term
Round Robin policy is biased against IO bound processes
Definition
true
Term
Virtual Round Robin policy is not biased against IO bound processes
Definition
true
Term
In Virtual Round Robin policy, the scheduler picks a process from auxillary queue if it has one.
Definition
true
Term
In Virtual Round Robin policy, a process remembers how much of its last time quantum it was not able to use.
Definition
true
Term
Shortest Process Next policy is biased against long processes.
Definition
true
Term
Shortest Remaining Time policy is biased against long processes.
Definition
true
Term
Highest Response Ratio Next policy is biased against long processes.
Definition
false
Term
Feedback scheduling is biased against long processes if the scheduler always picks a process from the non-empty highest priority queue.
Definition
true
Term
Fairshare scheduling allows a process to forget about its past CPU usage.
Definition
true
Term
Fairshare scheduling penalizes a process for the CPU usage by other processes in its group.
Definition
true
Term
CPU utilization efficiency is not as critical a factor for multiprocessor scheduling as it is for uniprocessor scheduling.
Definition
true
Term
It does not matter whether a process always executes on the same CPU or not.
Definition
false
Term
Load sharing is geared towards efficiently utilizing each CPU.
Definition
true
Term
Gang scheduling explictly ensures that all threads of a process/gang run together
Definition
true
Term
A CPU might stay idle for long times under gang scheduling.
Definition
true
Term
Determinism in a realtime system is measured by how quickly could the system recognize a received interrupt.
Definition
true
Term
Responsiveness in a real time system is measured by how quickly could the system process a received interrupt (after recognizing it).
Definition
true
Term
RMS guarantees meeting as many deadlines as EDF.
Definition
false
Term
RMS is based on converting the periodicity of a real-time task into its priority
Definition
true
Term
In RMS, the processes are scheduled as per their priority.
Definition
true
Term
In EDF, the processes are scheduled in the order of their deadlines
Definition
true
Term
In Linux, the non-real time processes are characterized as either interactive or batch.
Definition
true
Term
In Linux, a higher priority process can preempt a lower priority process from the CPU right away.
Definition
true
Term
In Linux, the time quantum assigned to a process depends on its static priority.
Definition
true
Term
In Linux, the real-time processes can have priority levels between 0 and 99 and are scheduled as per either FIFO or round-robin discipline.
Definition
true
Term
In Linux, the non-real time processes can have static/dynamic priority between 100 and 139.
Definition
true
Term
In Linux, the dynamic priority of a process can vary in the range (+5,-5) around the static priority.
Definition
true
Term
In Linux, the dynamic priority of a process decreases (in numerical value) with the increase in the average sleep time.
Definition
true
Term
A process with static priority 100 is considered interactive when its average sleep time exceeds 200ms.
Definition
true
Term
In Linux, a process with static priority 139 is never considered interactive.
Definition
true
Term
Linux uses a virtual round robin policy where an expired process (the process that has finished its time quantum) does not get executed until all processes have expired.
Definition
true
Term
In linux, real-time processed do not expire.
Definition
true
Term
In Linux, interactive processes generally get a fresh time quantum as soon as they finish their current one.
Definition
true
Term
In linux, a runqueue refers to the set of TASK_RUNNING processes currently bound to a particular CPU.
Definition
true
Term
In Linux, the next process to run on a CPU is the one at the head of the highest priority non-empty active queue.
Definition
true
Term
In Linux, an idle CPU migrates some processes from a busy CPU.
Definition
true
Term
Linux, multiple levels of scheduling domains allow CPUs to be grouped as per their "proximity".
Definition
true
Term
An idle CPU looks for work starting with CPUs in its lowest level scheduling domain.
Definition
true
Term
Fixed sized partitions suffer from internal fragmentation.
Definition
true
Term
Dynamic partitions suffer from external fragmentation.
Definition
true
Term
First fit algorithm is better than next fit and best fit in terms of the frequency of compaction.
Definition
true
Term
Buddy system eliminates both internal and external fragmentation.
Definition
false
Term
Buddy system amortizes the cost of partition creation and deletion.
Definition
true
Term
Logical to physical address translation in a segmentatio based system involves adding the offset to the beginning address of the segment.
Definition
true
Term
Logical to physical address translation in a paging based system involves replacing the page number with the corresponding frame number.
Definition
true
Term
Virtual memory allows a process to execute even if the complete process image is not in main memory.
Definition
true
Term
Resident set refers to the part of process image in main memory.
Definition
true
Term
Locality of reference means that the information a process will use in near future is likely to be near the information the process accessed in near past.
Definition
true
Term
Keeping only a part of the process in main memory won't work in environments where the locality of reference does not hold.
Definition
true
Term
Thrashing refers to processes having too little memory and hence issuing too many page faults.
Definition
true
Term
The root page table in a multilevel page table always needs to be in memory.
Definition
true
Term
A memory reference might involve 3 page faults if a 3-level page table is being used.
Definition
true
Term
Inverted page table uses chain of frames to support multiple pages mapping to the same frame number.
Definition
true
Term
Translation lookaside buffer is a fast cache for recently used page table entries.
Definition
true
Term
TLB uses associative memory.
Definition
true
Term
Large page size means smaller page tables.
Definition
true
Term
Large page size means more internal fragmentation.
Definition
true
Term
Small page size allows a process to keep only immediately useful information in memory.
Definition
true
Term
Prepaging refers to bringing pages in memory in anticipation that they will be used.
Definition
true
Term
In general, it does not matter which frame a particular page sits in.
Definition
true
Term
The best page to replace is the one least likely to be used in near future.
Definition
true
Term
LRU page replacement policy is based on the assumption that the least recently used page is the one least likely to be used in near future.
Definition
true
Term
The clock page replacement policy is based on LRU policy with page timestamps compressed to just one bit.
Definition
true
Term
In a clock based page replacement policy, the best page to replace is the one with used and modified bits zero.
Definition
true
Term
When a page is selected to be replaced, its frame is usually added to the list of free frames and incoming page actually sits in a different frame.
Definition
true
Term
Use of the scheme described in the previous question allows a replaced page to be quickly reclaimed if it is needed in near future.
Definition
ture
Term
In variable allocation, local scope policies to determine resident set size, the working set refers to the set of pages referred by the process in recent past.
Definition
true
Term
In variable allocation, local scope policies for determining the resident set size, the goal is to make resident set same as the working set.
Definition
true
Term
In page fault frequency algorithm to determine the resident set size, the resident set can balloon up whenever there is a shift to a new locality.
Definition
true
Term
In variable interval sampled working set strategy, only a certain number of page faults are allowed to occur between sampling instants (when pages with use bit 0 are kicked out).
Definition
true
Term
Variable interval sampled working set strategy avoids the ballooning policy associated with the page fault frequency algorithm.
Definition
true
Term
Precleaning refers to writing dirty pages back to hard disk while they are still in main memory.
Definition
true
Term
Precleaning will be useless if the cleaned up pages become dirty again while they are still in main memory.
Definition
true
Term
The level of multiprogramming can be dynamically adjusted based on the page fault rate the system is experiencing.
Definition
true
Term
Regular paging in 80x86 architecture divides the 32 bit logical address in 3 parts: 10-bit directory,10-bit table and 12-bit offset.
Definition
true
Term
In 80x86 architecture, the PCT flag in a page table entry specifies whether the page can be put in a CPU cache or not.
Definition
true
Term
In 80x86 architecture, the PWD flag in a page table entry specifies whether the page follows write back policy or write throough policy if it is put in a cache.
Definition
true
Term
Write back policy means that the page is modified only in cache and not in memory when it is written to.
Definition
true
Term
Write through policy means that, when a page in cache is modified, both in-memory and in-cache copies are modified.
Definition
true
Term
Cache coherence problem deals with making sure that copies of a page in different CPU caches stay synchronized.
Definition
true
Term
Extended paging in 80x86 architecture allows pages to be 4 MB in size.
Definition
true
Term
In 80x86 architecture, basic paging uses 2-level page tables whereas extended paging uses single level page tables.
Definition
true
Term
Physical Address Extension (PAE) allows an 80x86 machine to use upto 64 GB of memory.
Definition
true
Term
PAE is based on the use of 36 bit physical addresses.
Definition
true
Term
In PAE, the logical addresses are still 32 bits.
Definition
true
Term
In PAE, each page table entry is 8-bytes long.
Definition
true
Term
In PAE, the directory and table part of a logical address are 9-bits each.
Definition
true
Term
In PAE, each process can access upto 16GB of memory.
Definition
true
Term
PAE with 4KB pages uses a 3-level page table with a 2-bit indicator of the entry in the Page Directory Pointer Table at the top level.
Definition
true
Term
The largest page size available with PAE is 2 MB because only 20 bits are available in a logical address to indicate offset within a page.
Definition
true
Term
In PAE, the cr3 register specifies the Page Directory Pointer Table used by a particular process.
Definition
true
Term
In 64-bit 80x86 architecture, only 48 bits (out of total 64) are actually used for physical addresses.
Definition
true
Term
64-bit 80x86 architecture uses 4-level page tables.
Definition
true
Term
Linux adopts a common paging model that fits both 32-bit and 64-bit architectures.
Definition
true
Term
Linux uses 4-level page tables.
Definition
true
Term
For 32-bit architectures with no Physical Address Extension, Linux allocates 0 bits each to the Page Upper Directory and the Page Middle Directory fields in a logical address, thereby effectively using 2-level page tables.
Definition
true
Term
For 32-bit architectures with the Physical Address Extension enabled, Linux uses 3-level page tables by eliminating the Page Upper Directory.
Definition
true
Term
Programmed IO can lead to very poor CPU utilization.
Definition
true
Term
Interrupt driven IO could be very inefficient if large amounts of data needs to be transferred.
Definition
true
Term
DMA based IO involves CPU only at the beginning and the end of an IO operation.
Definition
true
Term
A DMA module could control just one IO device or several.
Definition
true
Term
DMA modules could be connected in many configurations either having their own separate bus to communicate with IO device(s) or sharing the system bus with the CPU.
Definition
true
Term
Reading from an IO device directly in to a frame in process space may be problematic since the frame might be taken away from the process.
Definition
true
Term
Using two or more IO buffers to read information from IO device could help reduce the IO wait times for a process.
Definition
true
Term
Smaller disk size means smaller seek time.
Definition
true
Term
If the disk rotates faster, the disk access time would be reduced.
Definition
true
Term
Disk scheduling policies aim to minimize the seek times for various disk read/write requests.
Definition
true
Term
FIFO is the best disk scheduling policy.
Definition
false
Term
In SCAN and C-SCAN disk scheduling policies, the read/write head moves in just one direction until it reaches the very end.
Definition
true
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