1. Software Architecture in Practice
Architecture and Performance Factors

2. Introduction
In Performance Engineering it is important to understand the factors of the Architecture that determines performance of your solution.
In this presentation the most common factors are presented.
A basic understanding of queuing theory is useful for understanding the impact these factors can have on performance.

3. Performance Factors
In the following slides we will look at some factors layer by layer. Since we cannot consider everything we will use the architecture of the TM16 application as basis
Hardware
Operating system
Application Server
Application
Database
Network

4. Hardware The “big four”
Processor
no. or processors, no. of cores, hyper-threading, processor speed, cache
Memory
Amount of physical memory, paging, memory speed
Disk I/O
Disk speed, RAID configuration, local disk vs. network disk
Network I/O
Network interface speed, protocol, network bandwidth
A good explanation of how to monitor these under windows can be found here:
Performance “hotspots” are typically detected from utilization and queue lengths
E.g. processor utilization, disk queue length etc.

5. Operating System
Depending on the solution there is typically a number of configuration options to be made, e.g.
Size of virtual memory, network buffer sizes, number of available TCP/IP ports, etc.
Operating system services can also impact performance
Unnecessary ones should be disabled
Necessary ones should be scheduled to cause minimum impact on your application
Eg. run outside office hours or give lower priority
Virtualization
In later years virtualized servers has become more common so majority of hosted solutions are now virtualized
In general virtualization systems do not constrain performance significantly, but you should know when you run virtualized – since you might not have the capacity you think

6. Application Server
An application server is a server that provides software applications with services such as security, data services, transaction support, load balancing, and management of large distributed systems.
The term is often used for web servers that support the Java Platform, Enterprise Edition, however its use isn't restricted to Java.
Performance tuning generally starts with the Java Virtual Machine (JVM), which serves as the foundation for the application server.
Depending on the services used by your application you will tune
Number of Application Server instances (JVM’s)
JVM heap size
Thread pool size
Connection pool size
Caches ….

7. Application
The application design has a major impact on the performance of your system.
In general you should focus on minimizing the work involved in moving data from database to the user
Don’t have too many layers
Client must not be too chatty with the server
Don’t fetch more data than necessary from database – and don’t visit other components when not needed
We will look more into patterns and anti-patterns in a later session

8. Database
Most applications use a relational database for data storage. The database is a very common cause of performance issues which are typically rooted in two different aspects
The configuration/structure of the RDBMS and the database
The applications’ use of the database
The query optimizer is an important piece of every DBMS.
It determines how your SQL expression will fetch the data you ask for.

9. Database optimization
Database optimization is a complex task beyond the scope of this class. Knowing about the basics is however a critical skill for performance engineers.
You always need to consider these aspects:
Keep database statistics up-to-date
Build appropriate indexes
Do the work on data as close to the data as possible
Consider stored procedures for large volumes of data
Only retrieve the data needed from the database
SELECT only the columns and rows needed
Use WHERE clauses to filter data
Use parameterized queries
SELECT x from user where name=‘?’
Partition large databases

10. Henrik Bærbak Christensen
… note
And quite a few of these rules do not apply to NoSQL databases …
Henrik Bærbak Christensen

11. Network
There is typically a number of networks involved between end users and the components of your application
For any network the two primary factors to consider are
Latency
Transmission speed
These are impacted by a number of factors, e.g.
Protocol
Number of “hops” from end-2-end
Network utilization
Network security (e.g. SSL)
Amount of messages exchanged
Message sizes
Network packet sizes ….

12. A few words on Java
When using the Java programming language there are a number of subjects you should be aware of
Garbage collector algorithm
Heap sizes
Temporary objects creations
Object retention leaks ….
A good way to investigate the inner workings of your Java application – and to learn more about general JVM performance – is to use a java code profiler
JDK contains a powerful graphical profiler jvisualvm
There are a wealth of good guides on the internet describing JVM performance, e.g.