A method for monitoring the quality-of-service (QoS) of high priority transactions in a software system includes receiving a specific QoS metric of a high priority transaction, where the QoS metric associated with a plurality of buckets and comparing the sampled specific QoS metric to an expected value for the specific QoS metric. If the sampled specific QoS metric exceeds the corresponding expected value, a bucket for the specific QoS metric is incremented, otherwise the bucket is decremented. If the bucket for the specific QoS metric overflows, the current bucket is reinitialized to zero, a depth of a next bucket for the specific QoS metric is computed, and a number of standard deviations from a mean value for the specific QoS metric is incremented. When the bucket for the specific QoS metric exceeds a threshold, a software rejuvenation routine is executed.