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| author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
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| committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
| commit | d796c9dd933ab96ec83b9a634feedd5d32e1ba3f (patch) | |
| tree | 6e3dcca4f77e20ec8966c666aac7c35bd4704053 /doc/html/emb-performance.html | |
| download | tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.tar.gz tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.zip | |
Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731
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| -rw-r--r-- | doc/html/emb-performance.html | 132 |
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diff --git a/doc/html/emb-performance.html b/doc/html/emb-performance.html new file mode 100644 index 000000000..51904cf19 --- /dev/null +++ b/doc/html/emb-performance.html @@ -0,0 +1,132 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/qws.doc:532 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>TQt/Embedded Performance Tuning</title> +<style type="text/css"><!-- +fn { margin-left: 1cm; text-indent: -1cm; } +a:link { color: #004faf; text-decoration: none } +a:visited { color: #672967; text-decoration: none } +body { background: #ffffff; color: black; } +--></style> +</head> +<body> + +<table border="0" cellpadding="0" cellspacing="0" width="100%"> +<tr bgcolor="#E5E5E5"> +<td valign=center> + <a href="index.html"> +<font color="#004faf">Home</font></a> + | <a href="classes.html"> +<font color="#004faf">All Classes</font></a> + | <a href="mainclasses.html"> +<font color="#004faf">Main Classes</font></a> + | <a href="annotated.html"> +<font color="#004faf">Annotated</font></a> + | <a href="groups.html"> +<font color="#004faf">Grouped Classes</font></a> + | <a href="functions.html"> +<font color="#004faf">Functions</font></a> +</td> +<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>TQt/Embedded Performance Tuning</h1> + + +When building embedded applications on low-powered devices, a number +of options are available that would not be considered in a desktop +application environment. These options reduce the memory and/or CPU +retquirements at the cost of other factors. +<p> <ul> +<li> <a href="emb-features.html"><b>Tuning the functionality of TQt</a> +<li> <a href="#general">General programming style</a> +<li> <a href="#static">Static vs. Dynamic linking</a> +<li> <a href="#alloc">Alternative memory allocation</a> +</ul> +<p> <a name="general"></a> +<h2> General programming style +</h2> +<a name="1"></a><p> The following guidelines will improve CPU performance: +<ul> +<li> Create dialogs and widgets once, then <a href="qwidget.html#hide">TQWidget::hide</a>() and +<a href="qwidget.html#show">TQWidget::show</a>() them, rather than creating them and deleting +them every time they are needed. +This will use a little more memory, but will be much faster. +Try to create them the first time "lazily" to avoid slow +startup (e.g. only create a Find dialog the first time the +user invokes it). +</ul> +<p> <a name="static"></a> +<h2> Static vs. Dynamic linking +</h2> +<a name="2"></a><p> A lot of CPU and memory is used by the ELF linking process. You can +make significant savings by using a static build of your application +suite. This means that rather than having a dynamic library (<tt>libqte.so</tt>) and a collection of executables which link dynamically to +that library, you build all the applications into a single executable +and statically link that with a static library (<tt>libqt.a</tt>). This +improves start-up time, and reduces memory usage, at the expense of +flexibility (to add a new application, you must recompile the single +executable) and robustness (if one application has a bug, it might +harm other applications). If you need to install end-user +applications, this may not be an option, but if you are building a +single application suite for a device with limited CPU power and +memory, this option could be very beneficial. +<p> To compile TQt as a static library, add the <tt>-static</tt> options when +you run configure. +<p> To build your application suite as an all-in-one application, design each +application as a stand-alone widget or set of widgets, with only minimal +code in the main() function. Then, write an application that gives +some way to switch between the applications (e.g. a <a href="qiconview.html">TQIconView</a>). +<a href="http://www.trolltech.com/products/qtopia/index.html">TQtopia</a> is an example of this. It can be built either as a set of +dynamically linked executables, or as a single static application. +<p> Note that you should generally still link dynamically against the +standard C library and any other libraries which might be used by +other applications on your device. +<p> <a name="alloc"></a> +<h2> Alternative memory allocation +</h2> +<a name="3"></a><p> We have found that the libraries shipped with some C++ compilers on +some platforms have poor performance in the built-in "new" and "delete" +operators. You might gain performance by re-implementing these +functions. For example, you can switch to the plain C allocators +by adding the following to your code: +<p> <pre> + void* operator new[]( size_t size ) + { + return malloc( size ); + } + + void* operator new( size_t size ) + { + return malloc( size ); + } + + void operator delete[]( void *p ) + { + free( p ); + } + + void operator delete[]( void *p, size_t size ) + { + free( p ); + } + + void operator delete( void *p ) + { + free( p ); + } + + void operator delete( void *p, size_t size ) + { + free( p ); + } +</pre> + + +<!-- eof --> +<p><address><hr><div align=center> +<table width=100% cellspacing=0 border=0><tr> +<td>Copyright © 2007 +<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a> +<td align=right><div align=right>TQt 3.3.8</div> +</table></div></address></body> +</html> |