Performance Performance is about time and the software system’s ability to meet timing requirements.

Performance Event arrival patterns: Periodic: events arrive predictably at regular time intervals. Stochastic: events arrive according to some probabilistic distribution. Sporadic: events arrive according to a pattern that is nether periodic nor stochastic. Response measures: Latency: the time between the event arrival and the system’s response. Deadline: for complete processing Throughput: number of transactions that the system can process in a unit time Jitter: allowable variation in latency Miss rate: the number of events that the system is not able to process Response time: Processing time: when the system is working to response by consuming resources Blocked time: when the system is unable to response, because of resource contention Contention for resources Availability of resources Dependency on other computation

Performance Tactics

Control Resource Demand by reducing the number of events processed Manage sample rate: reduce the sampling frequency Limit event response: process events only up to a set maximum rate Prioritize events: impose a priority scheme that ranks all events according to their importance for services Reduce overhead: remove intermediaries to improve latency (conflict with modifiability) Bound execution times: place a limit on how much execution time is used to response to an event Increase resource efficiency: improving the algorithms used in critical areas to decrese latency

Performance Tactics Manage Resources Increase resources: add additional hardware resources Introduce concurrency: do parallel processing when possible and not extra overhead Maintain multiple copies of computations: use multiple/replicated servers Maintain multiple copies of data: use caching and data replication Bound queue size: control the maximum number of queued arrivals and the resources used to process the arrivals. Need to deal with overflow. Schedule resources: understand the characteristics of each resource’s use and choose the scheduling strategy that is compatible with it.