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diff --git a/doc/assignment1.md b/doc/assignment1.md index 75324df..1fc8d5f 100644 --- a/doc/assignment1.md +++ b/doc/assignment1.md @@ -142,6 +142,23 @@ Instructions: Please answer the following questions in complete sentences. Your kernel mode. 1. Define cache, and explain cache coherency. + + The cache acts as a faster storage system that can store items on a temporary basis. + When a piece of data is needed, the cache can be used to fetch the data once + and stored in the cache. Subsequent attempts to access the same data can be + fetched from the cache at a faster rate of access. Cache is meant to be temporary + for fetching frequently used data quickly. However, the cache can become stale + and out of sync with the backing storage from where the cache initially retrieved + the data. Cache expiration is one of the hard problems in computer science. + + In a multitasking environment if several processes wish to access a piece of data + then each process must access the current value of that piece of data. If that + piece of data is stored in different caches it is possible for the same piece + of data to have a different value if there isn't a mechanism to synchronize each + of the caches with any mutations made to the piece of data. Cache coherency + ensures that the data stored in different layers of cache are synchronized and + this is typically handled in the hardware layer. + 1. Describe why direct memory access (DMA) is considered an efficient mechanism for performing I/O. 1. Describe why multicore processing is more efficient than placing each processor on its own chip. 1. Describe the relationship between an API, the system-call interface, and the operating system. |