Chapter 1: Introduction  Measurement and diagnosis tools

Chapter 1: Introduction

Determining factors

Several factors determine how well your application and server configuration perform.


Response time

Response time is the time required to execute a specified task, for example, to call an EJB method or submit a JSP form request. For end users, response time provides the key measurement of performance.

In client-side coding, you can minimize perceived response time by displaying partial results or status bars. However, in server-side coding, all you can do is minimize the in-server response time to an acceptable level. It helps to break down the response time into time spent in each component and subsystem. Figure 1-1 illustrates the processing of a Web form request to a JSP that calls an EJB component which in turn executes a remote database query. A slowdown can occur in any of these components. When tuning, you must isolate the part of your deployment that is causing the delay.

Figure 1-1: Response time breakdown


Scalability and throughput

Although a server configuration may perform well with a few users, response times can increase as the number of connected users increases. Scalability is a measure of how many simultaneous users your application and server configuration can support under prescribed use patterns before response times increase to unacceptable levels. Throughput is a measure of how many operations the server or application can process in a given time period; for example, database transactions per second or Web server page requests per second.

Throughput can be useful in comparing benchmark results for servers from different vendors, but scalability is a more useful measurement for tuning a given application deployment. You can directly measure the number of users and response times. End users are usually more concerned about how quickly their own work gets done than they are about overall server performance.


Memory use

Many performance optimizations in EAServer use caching: once created, objects such as component instances and database server connections are pooled for reuse, avoiding the overhead of re-creating the object. EAServer also caches servlet responses and static HTTP pages to avoid the overhead of running the servlet or reading files from disk, respectively. Caching reduces response time at the expense of increased memory use.

To maximize the performance gain from caching, Sybase recommends you run EAServer with as much memory as possible, from 1GB minimum for large deployments up to the limit of the machine architecture (4GB on most 32-bit address systems).

Common performance problems related to memory use include:


Threading

EAServer scales well, primarily through the use of native platform threads. Threading allows multiple components to execute concurrently with a minimum of context-switching overhead. Threading issues that affect performance include:





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