Characterizing the Storage Process and Its Effect on the Update of Main Memory by Write Through
Alan Jay Smith · Journal of the ACM · 1979
The problem of multiple, nonidentical copies of the same data in computer systems with both local cache and shared main memory has led some manufacturers to use "write-through" updating for main memory despite some known efficiency advantages favoring "swap" updating We propose that write throughs to main memory be buffered, thus reducing the probability that the CPU will have to walt for a mare memory write operation to take place Statistics on the nonstatmnary point process of stores to memory lead to a model in which the sequence of stores is considered to be described by a Poisson process which proceeds at rate ~, for a fraction of the Ume 13, This type of process has been described as a regime process Values for X, and /3, are obtained by (least squares) fitting the distrnbutlon function for the number of stores per 100 memory cycles This model is a model for the effect of the storage process on write-through updating, but is not a model of the storage process itself The model is then used to estimate the frequency of blocking in a computer system using a finite queue to buffer write-through operations The predicted frequency of blocking is found to agree well with the actual frequency of blocking as determined by trace driven simulation Comparisons are made with swap updating.