Overview
This
simple performance document covers the basics of performance testing. This
information may be useful for beginner who might be to start performance
testing.
The
analysis of the effectiveness, speed of a software system under varied load in
terms of throughput and response time is known as performance testing. What is performance testing?
Types of performance testing:
1.
Load Testing
2.
Stress Testing
3.
Scalability Testing
4.
Capacity Testing
Before we begin to study about performance testing we need to understand following terms.
Load Testing – a measurement of
the usage of the system. A server is said to experience “high load” when its
supported application is being heavily trafficked. It is done to identify the
application bottlenecks.
The purpose of load
testing is to ensure that your application will have a good response time
during peak usage.
Stress
Testing – Idea behind the
stress testing to check how any system gets exhausted when load is increased
substantially without adding any extra resource to handle such a high load.
Failure due stress test may be or may not be attended but this test is done to
identify the behavior of the system under stress.
Scalability
Testing -
Utilization of extra hardware resources to improve the response time is known
as scalability.
There are two types of scalability.
- Vertical Scalability
- Horizontal Scalability
Vertical scalability – It is the ability to increase the capacity of
existing hardware or software by adding resources - for example, adding
processing power, RAM to a server to improve response time.
Horizontal scalability – It is connecting multiple
servers so that they work as a single logical server to improve the response
time.
We perform scalability testing to determine how
effectively your Web site will expand to accommodate an increasing load.
Scalability testing allows you to plan Web site capacity improvements as your
business grows and to anticipate problems that could cost you revenue down the
line. Scalability testing also reveals when your site cannot maintain good
performance at higher usage levels, even with increased capacity.
Capacity
Testing (Volume) - Capacity Testing is
performed to determine maximum load limits that a system can handle to meet the
desired business processing. You can define the capacity of the system under a
suggested hardware and software configuration beyond which the system will
fail.
A Process for performance testing
Performance testing
you can do in following manner:
- Complete the entire functional test to
ensure that your application is working properly to perform the
performance test.
- Select a suitable tool for your
application
- Write test scripts to populate database
sufficient amount of data.
- Write test script to cover the main
functionality and transaction of the application.
- Run performance tests scripts to measure
response time and throughput.
- Then apply varying load as desired.
- Run your performance tests again.
- If response times are significantly
larger for the second test, then something is wrong.
- Once you have tested the application
with varying load then compare their response times. These can be easily
measured by load testing tools.
- Now you can now
interpret the results and make predictions based on the average response
time of these tests and the resource utilization of the server during the
tests.
- After identifying
problems area in the application you can make suggestions for optimization
of the hardware and software resources.
Why we need Performance testing?
Load,
Capacity, scalability and stress testing eliminates real time surprises and
ensures that your web site will be able to perform this way under this much
load. Without doing the performance testing it is very hard to know what might
happen when your site has to perform under a heavy load.
There
are following reasons which impose you to carry out the performance testing
putting you site to real world.
- To know how much
traffic your site can handle.
- To know what end
users will experience when traffic becomes heavy.
- Helps to Maximize
Your Application Performance -
Performance testing can measure performance
response times and availability from the end-user’s perspective. This allows
you to quickly identify performance problems and keep your end users happy
under all load conditions.
- Pinpoint
Performance Bottlenecks -
You can watch your web application respond to
load testing
and observe bottlenecks in action. Real-time performance monitors allow the
experts to instantly identify bottle-necks and discuss these findings with you.
Following the test, you can view reports online, complete with performance
graphs.
How to improve Performance of your application?
You
know that performance of any application directly leads to reduce response time
and can be improved by following ways.
- Performance can
be increased through software optimization.
- Cut the average
transaction response time.
- Increase your
system maximum throughput (KB/sec).
- By doing load
balancing and server clustering.
- Eliminating
memory leaks
- Optimize
database query handling
- Improve network
bandwidth
- Improve network routing problem
- Remove
deadlock problem relating to a single threaded process.
Definitions related to performance testing
Response Time – It is the time taken between requests and received the
responses for same request.
Latency - It is the increases in
response delay beyond the time desired for an operation for any system. It can
also be described as delay in desired response time.
Throughput – It is a measure of
amount of data processed by any system over a period of time. Throughput can be
measured in kbps, mbps or gbps.
Hits/Second – It is a measure of
traffic flow to a server every second.
Virtual user - Virtual User (VU) is
an automated testing tool that allows a computer to emulate multiple real users
from a single computer system.
Transaction – It is transaction
usually means a sequence of information exchange and related work that is
treated as a unit for the purposes of satisfying a request.
CPU Load - The CPU load for a
system is the number of processors in the system.
CPU utilization - Monitoring counters such as %Processor Time
and Total Processor Time will give you a bigger picture of how your CPU is
handling the load. Your processor should not sustain a level of more than 80
percent for either of these counters. If it does, you need to look at upgrading
your processor or adding another processor, if the system allows for it.
Memory Leak – It is the gradual loss of available
computer memory when a program
repeatedly fails to return memory that it has obtained for temporary use. As a
result, the available memory for that application or that part of the operating
system becomes exhausted and the programs can no longer function. For a program
that is frequently opened or called or that runs continuously, even a very
small memory leak can eventually cause the program or the system to terminate.
A memory leak is the result of a program bug.
Some
operating systems provide memory leak detection so that a problem can be
detected before an application or the operating system crashes. Some program development tools also provide automatic "housekeeping" for the developer. It is always the best programming practice to return memory and any temporary file to the operating system after the program no longer needs it.
Load balancing - It is the distribution of the load from a single web server to multiple servers as single logical unit.
To achieve this you can either distributing the load:
1)
Evenly
among all the servers in the cluster
2)
Load
can be distributed by optimize the load on the server.
Server cluster – It is a group, combination of web server and
database. Clustering can be done with one or more servers at from and single
database at backend.
Performance Testing Tools
Most commonly used
automation testing tools are:
HP - Load runner,
Astra load
Segue – Silk
Performer
Rational –Performance
Studio, Performix, Robot (VU)
Empirix – e-Test,
e-Load
Microsoft – WCAT (Web Capacity Analysis Tool), WAST (Web Application
Stress Tool)
Compuware – QALoad
Cyrano – Open STA
RadView - WebLoad
