Swift FS has some simple duration counting classes which are used to track HTTP performance, with incremental creation of mean, min, max and variance. These are not moving averages, simply ongoing over time. They've proved useful in detecting which operations are slowest against objects stores. (it turned out to be delete throttling in test teardown BTW, showing the value of the instrumentation)
By moving them into utils, all the object stores can build up some stats on cost of HTTP operations.