NEW Contents Flashcards
Requirements for ‘local replacement’ and ‘fixed allocation’.
Fixed number frames allocated to process.
Page to be replaced chosen from frames allocated to process.
Requirements for ‘local replacement’ and ‘variable allocation’.
Dynamic number of frames allocated to process from ttt.
Page to be replaced chosen from frames allocated to process.
Requirements for ‘global replacement’ and ‘fixed allocation’.
Not possible.
Requirements for ‘global replacement’ and ‘variable allocation’.
Page to be replaced chosen from ALL frames allocated to process.
What is the relationship between FIFO and clock page replacement algorithms?
Clock policy similar to FIFO, BUT, any frame with bit ‘1’ is passed over by algorithm.
Suppose the virtual space access by emory is 6GB, the page size is 8KB, and each page table entry is 6bytes. Compute the number of virtual pages that is implied. Also compute the space required for the whole page table.
Size of page table = page size x page table entry
=8 x 1024 x 6
=49152 bytes
=48KB
No. virtual pages = virtual space / page size
=6 x 1024 x 1024 / 8
=786432
How does DMA increase system concurrency? How does it complicate hardware design?
Allows CPU to perform tasks WHILE DMA system transfers data via system and memory buses.
Complicated -> DMA controller must be integrated into system, and allow DMA controller to be master of memory buses
Explain the purpose of open and close operations. What do open and close do?
Open informs system that the file is about to become active. Creates BUFFERS, DATA CONTROL BLOCKS, DATA STRUCTURES.
Close informs system that the file is about to become inactive. Outputs LAST BUFFER of information, deletes BUFFERS, DATA CONTROL BLOCKS, DATA STRUCTURES
List 3 ways of allocating storage, and give advantages of each.
1) CONTIGUOUS - fastest, if no changes. Easiest random access.
2) LINKED - no external fragmentation. File grows without complications
3) INDEXED - direct access. Simplifies file position placement
