Common Design Patterns for Symbian OS: The Foundations of Smartphone Software

A.3. Run-time Impact of Increased Code Size

Increasing the code size of an executable can impact the following system characteristics:^[]

^[] Characteristics, such as maintainability, testability, etc., can also be influenced by having more code but they're not significantly influenced by how the device is configured.

• The executable takes up additional disk space.

• More RAM is needed to load the executable.

• Loading the executable takes longer.

However, which characteristics are impacted and to what degree varies according to how the device is configured and what technologies it uses. Table A.2 summarizes the determining factors.

Table A.2. Factors Affecting the Run-time Impact of Increased Code Size

Potential Impacts of Increased Code Size	Device Configuration
	XIP	Non-XIP
		Moving Memory Model	Multiple Memory Model	Code is Demand Paged
Disk space	Particularly impaired	Impaired	Impaired	Impaired
RAM usage	No significant impact	Increases	Increases independently of how many processes use the code	Reduces impact of the memory model
Time to load the code	No significant impact	Impaired	Impaired	Variable (see below)

As you can see the most important factor is whether the code is loaded from XIP or non-XIP flash. If it's on XIP flash then the Loader has to do very little to enable the code to be executed. If the code is on non-XIP flash then, by definition, the code cannot be executed in place and the Loader has to allocate RAM in which to hold the code that will be executed. In addition, it's not a simply case of ...