Performance engineering encompasses the techniques applied during a systems development life cycle to ensure the

non-functional requirement In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviours. They are contrasted with funct ...

s for performance (such as

throughput Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ove ...

, latency, or

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...

usage) will be met. It may be alternatively referred to as systems performance engineering within

systems engineering Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design, integrate, and manage complex systems over their life cycles. At its core, systems engineering utilizes systems thinki ...

, and software performance engineering or application performance engineering within

software engineering Software engineering is a systematic engineering approach to software development. A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...

. As the connection between application success and business success continues to gain recognition, particularly in the mobile space, application performance engineering has taken on a preventive and perfective"Banking Industry Lessons Learned in Outsourcing Testing Services," Gartner. August 2, 2012. role within the software development life cycle. As such, the term is typically used to describe the processes, people and technologies required to effectively test non-functional requirements, ensure adherence to service levels and optimize application performance prior to deployment. The term ''performance engineering'' encompasses more than just the software and supporting infrastructure, and as such the term performance engineering is preferable from a macro view. Adherence to the non-functional requirements is also validated post-deployment by monitoring the production systems. This is part of

IT service management Information technology service management (ITSM) is the activities that are performed by an organization to design, build, deliver, operate and control information technology (IT) services offered to customers. Differing from more technology-o ...

(see also

ITIL The Information Technology Infrastructure Library (ITIL) is a set of detailed practices for IT activities such as IT service management (ITSM) and IT asset management (ITAM) that focus on aligning IT services with the needs of business. ITIL de ...

). Performance engineering has become a separate discipline at a number of large corporations, with tasking separate but parallel to systems engineering. It is pervasive, involving people from multiple organizational units; but predominantly within the

information technology Information technology (IT) is the use of computers to create, process, store, retrieve, and exchange all kinds of data . and information. IT forms part of information and communications technology (ICT). An information technology syste ...

organization.

Performance engineering objectives

*Increase business revenue by ensuring the system can process transactions within the requisite timeframe *Eliminate system failure requiring scrapping and writing off the system development effort due to performance objective failure *Eliminate late system deployment due to performance issues *Eliminate avoidable system rework due to performance issues *Eliminate avoidable system tuning efforts *Avoid additional and unnecessary hardware acquisition costs *Reduce increased

software maintenance Software maintenance in software engineering is the modification of a software product after delivery to correct faults, to improve performance or other attributes. A common perception of maintenance is that it merely involves fixing defects. H ...

costs due to performance problems in production *Reduce increased software maintenance costs due to software impacted by ad hoc performance fixes *Reduce additional operational overhead for handling system issues due to performance problems *Identify future bottlenecks by simulation over prototype *Increase server capability

Performance engineering approach

Because this discipline is applied within multiple methodologies, the following activities will occur within differently specified phases. However, if the phases of the rational unified process (RUP) are used as a framework, then the activities will occur as follows: During the first, Conceptual phase of a program or project, critical

business process A business process, business method or business function is a collection of related, structured activities or tasks by people or equipment in which a specific sequence produces a service or product (serves a particular business goal) for a parti ...

es are identified. Typically they are classified as critical based upon revenue value, cost savings, or other assigned business value. This classification is done by the business unit, not the IT organization. High level risks that may impact system performance are identified and described at this time. An example might be known performance risks for a particular vendor system. Finally, performance activities, roles and deliverables are identified for the Elaboration phase. Activities and resource loading are incorporated into the Elaboration phase project plans.

Elaboration

During this defining phase, the critical business processes are decomposed to critical

use case In software and systems engineering, the phrase use case is a polyseme with two senses: # A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful. # A potential scenario ...

s. Probe cases will be decomposed further, as needed, to single page (screen) transitions. These are the use cases that will be subjected to script driven performance testing. The type of requirements that relate to performance engineering are the non-functional requirements, or NFR. While a functional requirement relates to which business operations are to be performed, a performance related non-functional requirement will relate to how fast that business operation performs under defined circumstances.

Construction

Early in this phase a number of performance tool related activities are required. These include: *Identify key development team members as subject matter experts for the selected tools. *Specify a profiling tool for the development/component unit test environment. *Specify an automated unit (component) performance test tool for the development/component unit test environment; this is used when no GUI yet exists to drive the components under development. *Specify an automated tool for driving server-side unit (components) for the development/component unit test environment. *Specify an automated multi-user capable script-driven end-to-end tool for the development/component unit test environment; this is used to execute screen-driven use cases. *Identify a database test data load tool for the development/component unit test environment; this is required to ensure that the database optimizer chooses correct execution paths and to enable reinitializing and reloading the database as needed. *Deploy the performance tools for the development team. *Presentations and training must be given to development team members on the selected tools. The performance test team normally does not execute performance tests in the development environment, but rather in a specialized pre-deployment environment that is configured to be as close as possible to the planned production environment. This team will execute performance testing against

test case In software engineering, a test case is a specification of the inputs, execution conditions, testing procedure, and expected results that define a single test to be executed to achieve a particular software testing objective, such as to exercise ...

s, validating that the critical use cases conform to the specified non-functional requirements. The team will execute

load testing Load testing is the process of putting demand on a structure or system and measuring its response. Software load testing The term ''load testing'' is used in different ways in the professional software testing community. ''Load testing'' gene ...

against a normally expected (median) load as well as a peak load. They will often run stress tests that will identify the system bottlenecks. The data gathered, and the analysis, will be fed back to the group that does performance tuning. Where necessary, the system will be tuned to bring nonconforming tests into conformance with the non-functional requirements. If performance engineering has been properly applied at each iteration and phase of the project to this point, hopefully this will be sufficient to enable the system to receive performance certification. However, if for some reason (perhaps proper performance engineering working practices were not applied) there are tests that cannot be tuned into compliance, then it will be necessary to return portions of the system to development for refactoring. In some cases the problem can be resolved with additional hardware, but adding more hardware leads quickly to diminishing returns.

Transition

During this final phase the system is deployed to the production environment. A number of preparatory steps are required. These include: *Configuring the operating systems, network, servers (application, web, database, load balancer, etc.), and any message queueing software according to the base checklists and the optimizations identified in the performance test environment *Ensuring all performance monitoring software is deployed and configured *Running statistics on the database after the production data load is completed Once the new system is deployed, ongoing operations pick up performance activities, including: *Validating that weekly and monthly performance reports indicate that critical use cases perform within the specified non functional requirement criteria *Where use cases are falling outside of NFR criteria, submit defects *Identify projected trends from monthly and quarterly reports, and on a quarterly basis, execute

capacity planning Capacity planning is the process of determining the production capacity needed by an organization to meet changing demands for its products. In the context of capacity planning, design capacity is the maximum amount of work that an organization ...

management activities

Service management

In the operational domain (post production deployment) performance engineering focuses primarily within three areas:

service level management The Information Technology Infrastructure Library (ITIL) is a set of detailed practices for IT activities such as IT service management (ITSM) and IT asset management (ITAM) that focus on aligning IT services with the needs of business. ITIL de ...

capacity management Capacity management's goal is to ensure that information technology resources are sufficient to meet upcoming business requirements cost-effectively. One common interpretation of capacity management is described in the ITIL framework. ITIL vers ...

, and

problem management Problem management is the process responsible for managing the lifecycle of all problems that happen or could happen in an IT service. The primary objectives of problem management are to prevent problems and resulting incidents from happening, to ...

Service level management

In the service level management area, performance engineering is concerned with

service level agreement A service-level agreement (SLA) is a commitment between a service provider and a customer. Particular aspects of the service – quality, availability, responsibilities – are agreed between the service provider and the service user. ...

s and the associated systems monitoring that serves to validate service level compliance, detect problems, and identify trends. For example, when real user monitoring is deployed it is possible to ensure that user transactions are being executed in conformance with specified non-functional requirements. Transaction response time is logged in a database such that queries and reports can be run against the data. This permits trend analysis that can be useful for capacity management. When user transactions fall out of band, the events should generate alerts so that attention may be applied to the situation.

Capacity management

For capacity management, performance engineering focuses on ensuring that the systems will remain within performance compliance. This means executing trend analysis on historical monitoring generated data, such that the future time of non compliance is predictable. For example, if a system is showing a trend of slowing transaction processing (which might be due to growing data set sizes, or increasing numbers of concurrent users, or other factors) then at some point the system will no longer meet the criteria specified within the service level agreements. Capacity management is charged with ensuring that additional capacity is added in advance of that point (additional CPUs, more memory, new database indexing, et cetera) so that the trend lines are reset and the system will remain within the specified performance range.

Problem management

Within the problem management domain, the performance engineering practices are focused on resolving the root cause of performance related problems. These typically involve system tuning, changing operating system or device parameters, or even refactoring the application software to resolve poor performance due to poor design or bad coding practices.

Monitoring

To ensure that there is proper feedback validating that the system meets the NFR specified performance metrics, any major system needs a monitoring subsystem. The planning, design, installation, configuration, and control of the monitoring subsystem are specified by an appropriately defined monitoring process. The benefits are as follows: * It is possible to establish service level agreements at the use case level. * It is possible to turn on and turn off monitoring at periodic points or to support problem resolution. * It enables the generation of regular reports. * It enables the ability to track trends over time, such as the impact of increasing user loads and growing data sets on use case level performance. The trend analysis component of this cannot be undervalued. This functionality, properly implemented, will enable predicting when a given application undergoing gradually increasing user loads and growing data sets will exceed the specified non functional performance requirements for a given use case. This permits proper management budgeting, acquisition of, and deployment of the required resources to keep the system running within the parameters of the non functional performance requirements.