351 Operating System Word Scramble
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Question | Answer |
What is DMA | Direct Memory Access - used for large data movement |
What is blocking I/O? | blocking is when a processes is suspended until I/O completed. easy to use and understand but insufficient for some needs |
What is asynchronous I/O? | process runs while I/O executes |
What is buffering? | store data in memory while transferring between devices (1)To cope with device speed mismatch (2)To cope with device transfer size mismatch (3)To maintain “copy semantics” |
What is caching? | faster device holding copy of data Always just a copy Key to performance Sometimes combined with buffering |
What is the difference between buffering and caching? | |
What is stream? | |
How to improve performance of a computer system? (I/O) | |
What is non-blocking I/O? | I/O call returns as much as available. user interface, data copy(buffered I/O) implemented via multi-threading, returns quickly with count of bytes read or written, select() to find if data ready then read() or write() to transfer |
Double buffering | (1) two copies of the data, Kernel and user (2) Varying sizes, Full / being processed and not-full / being used (3)Copy-on-write can be used for efficiency in some cases |
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