Basic terms for Memory Hierarchy
Principle Of Locality: Most of the programs spends most of the time of their execution on small number of instructions such as Loops and functions.
Temporal Locality (Locality in time ): If any data item is referenced ,then it is likely to be referenced soon in future.
Spatial Locality (Locality in Space) :if any data item is referenced, then data items close to it are likely to be referenced in future.
Block : Minimum amount of information that can/ can not be present at any level of memory hierarchy.
Hit : Data requested by the processor is found at the required level of memory hierarchy.
Hit Rate : Fraction of memory accesses that are found in the required level of memory hierarchy.
Hit time : It is the total time, which includes the time to access the memory and time needed to determine whether the access is hit or miss i.e. time needed to look through all the blocks of the the particular level.
Miss : When the required data is not found in the particular level. The lower level ( level which is superset of the miss level ) is then accessed to retrieve the block containing the requested data.
Miss rate (1- Hit rate):the fraction of memory access that are not found in the particular level.
Miss penalty : Time to access the block in the lower level plus time to transmit the block from one to other level plus time to insert in to the level which observed the miss.