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A cache has two primary figures of merit: latency and hit ratio. A number of secondary factors also affect cache performance. [1] The hit ratio of a cache describes how often a searched-for item is found. More efficient replacement policies track more usage information to improve the hit rate for a given cache size.
In computing, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [ 2 ] A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value ...
Diagram of a CPU memory cache operation. In computing, a cache (/ kæʃ / ⓘ KASH) [ 1 ] is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A cache hit occurs when the ...
Cache performance measurement and metric. A CPU cache is a piece of hardware that reduces access time to data in memory by keeping some part of the frequently used data of the main memory in a 'cache' of smaller and faster memory. The performance of a computer system depends on the performance of all individual units—which include execution ...
AMAT's three parameters hit time (or hit latency), miss rate, and miss penalty provide a quick analysis of memory systems. Hit latency (H) is the time to hit in the cache. Miss rate (MR) is the frequency of cache misses, while average miss penalty (AMP) is the cost of a cache miss in terms of time. Concretely it can be defined as follows.
In Oracle 9i and earlier, it is 4 MB if the SGA size is less than 128 MB, and 16 MB otherwise. For later releases, it is typically 4 MB if the SGA size is less than 1 GB, and 16 MB otherwise. [3] There must be at least 3 granules in the SGA: one for the Database Buffer Cache, one for the Shared Pool Area and one for the Redo Log Buffer. It is ...
In computer science, a lookup table (LUT) is an array that replaces runtime computation with a simpler array indexing operation, in a process termed as direct addressing.The savings in processing time can be significant, because retrieving a value from memory is often faster than carrying out an "expensive" computation or input/output operation. [1]
Cache hierarchy, or multi-level cache, is a memory architecture that uses a hierarchy of memory stores based on varying access speeds to cache data. Highly requested data is cached in high-speed access memory stores, allowing swifter access by central processing unit (CPU) cores. Cache hierarchy is a form and part of memory hierarchy and can be ...