// is close to the limit, we want to make sure we push harder to keep it under, so
// if we target below the memory limit, we ensure that the background scavenger is
// giving the situation the urgency it deserves.
//
// In this case, the goal is defined as:
//    (100-reduceExtraPercent) / 100 * memoryLimit
//
// We compute both of these goals, and check whether either of them have been met.