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User Perception performance tips
Get rid of your performance problems and memory leaks!
Get rid of your performance problems and memory leaks!
This page details tips relevant to how best to present an application to your users
so that the application seems fast. Usability and the perception of speed are very
important aspects of performance.
The following pages have their detailed tips extracted below
The following detailed tips have been extracted from the raw tips page
Balancing Network Load with Priority Queues (Page last updated December 2001, Added 2002-02-22, Author Frank Fabian, Publisher Dr. Dobb's). Tips:
- Sort incoming requests into different priority queues, and service the requests according to the priorities assigned to each queue. [Article gives the example where combining user and automatic requests in one queue can result in a worst case user wait of 3.5 minutes, as opposed to less than 0.1 seconds if priority queues are used].
"Cutting Edge Java Game Programming". Oldish but still useful intro book to games programming using Java. (Page last updated 1996, Added 2001-06-18, Author Neil Bartlett, Steve Simkin , Publisher Coriolis). Tips:
- Make sure you have a throttle control that can make the game run slower (or pause) when necessary.
- If the cumulative downloading of your applet exceeds the player?s patience, you?ve lost a customer.
- The user interface should always be responsive. A non-responsive window means you will lose your players. Give feedback on necessary delays. Provide distractions when unavoidable delays will be lengthy [more than a few seconds].
- Latency between networked players can easily lead to de-synchronized action and player frustration. Displays should locally simulate remote action as continuing current activities/motions, until the display is updated. On update, the actual current situation should be smoothly resolved with the simulated current situation.
- Sending activity updates more frequently ensures smoother play and better synchronization between networked players, but requires more CPU effort and so affects the local display. In order to avoid adversely affecting local displays, send actvity updates from a low priority thread.
- It is usually possible to increase performance at the expense of image quality and accuracy. Techniques include reducing pixel depth or display resolution, field interlacing, aliasing. The key, however, is to degrade the image in a way that is likely to be undetectable or unnoticeable to the user. For example a moving player often pays less attention to image quality than a resting or static player.
J2EE Application server performance (Page last updated April 2001, Added 2001-04-20, Author Misha Davidson, Publisher Java Developers Journal). Tips:
- Good performance has sub-second latency (response time) and hundreds of (e-commerce) transactions per second.
http://www.bastie.de/resource/res/mjp.pdf and http://www.bastie.de/java/mjperformance/contents.html
Performance tuning report in German. Thanks to Peter Kofler for extracting the tips. (Page last updated November 2001, Added 2001-07-20, Author Sebastian Ritter, Publisher Ritter). Tips:
- use multiple threads to increase perceived performance
Application performance tuning (Page last updated July 2002, Added 2002-07-24, Author Baya Pavliashvili and Kevin Kline, Publisher informIT). Tips:
- Consider using "eye candy" to distract attention during acceptable short waits.
Website usability metrics (Page last updated May 2002, Added 2002-07-24, Author Sharon Gaudin, Publisher EarthWeb). Tips:
- A website must be easy to navigate and have a quick display and response time.
- Bad navigation metrics include: abandoned shopping carts; first time visitors look at one or two pages and disappear; dead ends require the "back" button; less than 5% buy something; any broken links.
- Good navigation metrics include: three pages or less from wesbite entry to desired information; no streaming video or Flash introductions; multiple ways to reach the required information; up to date search engines; basic compancy and contact info one click away from the homepage.
J2EE Performance tuning (Page last updated October 2001, Added 2001-10-22, Author James McGovern, Publisher Java Developers Journal). Tips:
- Performance is sometimes in perception: try to provide immediate feedback.
Coding standards with a small but interesting section (section 7.3) on optimizations (Page last updated January 2000, Added 2001-04-20, Author Scott Ambler, Publisher AmbySoft). Tips:
- Users are sensitive to particular delays: users will likely be happier with a screen that draws itself immediately and then takes eight seconds to load data than with a screen that draws itself after taking five seconds to load data.
- Give users immediate feedback: you do not always need to make your code run faster to optimize it in the eyes of your users.
- Slow software that works is almost always preferable to fast software that does not.
Website performance. (Page last updated October 2001, Added 2001-11-27, Author Gordon Benett, Publisher Intranet Journal). Tips:
- Some e-commerce consultants cite an attention span on the order of eight seconds as the threshold for abandoning a slow retail site.
- Where broadband connections are the norm, pages that don't appear instantly stand a good chance of never being seen: slow pages might as well be no pages.
Mobile & wireless devices (Page last updated April 2002, Added 2002-04-26, Author James White, Publisher Java Developers Journal). Tips:
- Attempt to create applications that can accomplish 80% or more of their operations through the touch of a single key/button or the "tap" or touch of the stylus to the screen.
- Trying to manipulate a very small scroll bar on a small screen can be an exercise in hand-eye coordination. Horizontal scrolling should be avoided at all costs. Use "jump-to" buttons rather than scrollbars.
- Try to avoid having the user remember any data, or worse, having to compare data across screens.
Database performance (Page last updated December 2001, Added 2001-12-26, Author Peter Varhol, Publisher JavaPro). Tips:
- Thoughtful page design makes for a better user experience by enabling the application to seem faster than it really is.
- Use the flush method associated with the out object to display static text and graphics on the browser page before the database query returns, to prevent the user from having to look at a blank page for a long time.
Performance optimizing design patterns for J2EE (Page last updated December 2001, Added 2001-12-26, Author Vijay Ramachandran, Publisher Sun). Tips:
- When you need to access a large remote list of objects, use the Page-by-Page Iterator pattern which sends smaller subsets of the data as requested until the client no longer want any more data. Use the Page-by-Page Iterator to send lists of simple objects from EJBs to clients.
Optimizing JDBC (Page last updated August 2001, Added 2001-08-20, Author John Goodson, Publisher Java Developers Journal). Tips:
- Retrieve data as efficiently as possible: Minimize the amount of data returned by the query; Don't make average users pay the same query cost of the users with extensive query requirements; Remember that users seldom want to see too much data in one go; Use setMaxRows(), setMaxFieldSize(), and SetFetchSize(); Decrease the column size; Use the smallest packet size that will meet your needs (if the driver supports packet sizing).
Servlet performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips:
- Flush the data in sections so that the user can see partial pages more quickly.
JSP performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips:
- Flush the data in sections so that the user can see partial pages more quickly.
Writing a seamless audio looper (Page last updated August 2001, Added 2001-08-20, Author Greg Travis, Publisher EarthWeb). Tips:
- Switching audio streams from one piece of sound to another requires some fiddly managing of the transition delay in order to avoid a gap in the audio output.
- To avoid the transition delay, you need to: flush the output buffer; find out how much data was dumped; add a fudge factor; and combine these values to determine from where to start playing the new audio stream.
Web application scalability. (Page last updated June 2000, Added 2001-05-21, Author Billie Shea, Publisher STQE Magazine). Tips:
- Avoid deploying an application server that will cause embarrassment, or that could weaken customer confidence and business reputation [because of bad response times or lack of calability].
Performance chapter (chapter 20) from "Professional JSP 2nd Edition" (Page last updated August 2001, Added 2001-10-22, Author Simon Brown, Robert Burdick, Darko Cokor, Jayson Falkner, Ben Galbraith, RodJohnson, Larry Kim, Casey Kochmer, Thor Kristmundsson, Sing Li, Dan Malks, Mark Nelson, Grant Palmer, Bob Sullivan, Geoff Taylor, John Timney, Sameer Tyagi, Geert Van Damme, Steve Wilkinson, Publisher The Server Side). Tips:
- The user's view of the response time for a page view in his browser depends on download speed and on the complexity of the page. e.g. the number of graphics. A poorly-designed highly graphical dynamic website could be seen as 'slow' even if the web downloads are individually quite fast.
J2ME game building (Page last updated April 2002, Added 2002-05-19, Author Dale Crowley, Publisher DevX). Tips:
- Smart graphics is important: you need to draw clear, concise images at extremely low resolutions and with very small palettes. Animated characters need dynamic, easily-read poses which avoid kicks looking like a dance steps, or punches looking like an arm waves.
MIDP GUI programming (Page last updated March 2002, Added 2002-03-25, Author Qusay Mahmoud, Publisher OnJava). Tips:
- Entering alphanumeric data through a handheld device can be tedious. If possible, provide a list of choices from which the user can select.
Another tutorial from Sun. This ones on animation (Page last updated ?, Added 2000-12-20, Author ?, Publisher Sun). Tips:
- Normal frame rates for animation: 8 frames per second (fps) for poor quality animation; 12 fps for standard animation; 24 fps for short bursts of smooth, realistic motion.
Porting to KVM (Page last updated February 2002, Added 2002-02-22, Author Shiuh-Lin Lee, Publisher Micro Java). Tips:
- Use selection lists rather than manual entry to speed up user data entry.
ftp://ftp.java.sun.com/docs/j2se/1.4/VolatileImage.pdf and http://www.javagaming.org/Docs/VolatileImageAPI.htm
Using VolatileImage (Page last updated May 2001, Added 2001-07-20, Author Someone@sun, Publisher Sun). Tips:
- Graphics performance in 1.2 is worse than 1.1. 1.3 is better, and 1.4 should be the fastest yet.
Chapter 1, "What Is Performance?" of "Java Platform Performance". (Page last updated 2000, Added 2001-11-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Tips:
- Perceived performance is a highly important aspect of performance. How fast a program feels is more important than how fast it really is.
Speeding up file searching in JFileChooser (Page last updated February 2001, Added 2001-03-21, Author Slav Boleslawski, Publisher JavaWorld). Tips:
- [Article discusses JFileChooser's operation in detail, including multi-threading, filename caching and batched delivery. Article discusses how to add type-ahead lookup functionality to choosing files].
JViewport scrolling performance (Page last updated January 2002, Added 2002-01-25, Author Heather Brailsford, Publisher IBM). Tips:
- JViewport.BLIT_SCROLL_MODE is the default scrolling mode for JViewport in SDK 1.3 (available since 1.2.2). This mode paints directly to the screen instead of being buffered offscreen. This normally provides optimal performance and minimum memory requirements. However complex images may display some intermediate paint operations if the painting is not fast enough, giving jerky or flashing images. If this is unacceptable, try the alternate modes: setScrollMode(BACKINGSTORE_SCROLL_MODE) (intermediate performance, higher memory requirements); or setScrollMode(JViewport.SIMPLE_SCROLL_MODE) (slowest).
Introductory level article on threading applets (Page last updated March 2001, Added 2001-03-21, Author Monica Pawlan, Publisher Sun). Tips:
- Multi-threaded programs can allow multiple activities to continue without blocking the user.
- Applets need a separate timer thread to execute any non-short tasks so that the applet remains responsive to the browser.
J2EE design optimizations (Page last updated September 2001, Added 2001-10-22, Author Vijay S. Ramachandran, Publisher Java Developers Journal). Tips:
- Don't transfer long lists of data to the user, transfer a page at a time (this is called the Page-by-Page Iterator pattern).
Choosing a J2EE application server, emphasizing the importance of performance issues (Page last updated February 2001, Added 2001-02-21, Author Steve Franklin, Publisher DevX). Tips:
- Decide on what is acceptable downtime for your application, and ensure the app server can deliver the required robustness. High availability may require: transparent fail-over; clustering; load balancing; efficient connection pooling; caching; duplicated servers; scalable CPU support.
Making HTTP connections using background threads. (Page last updated September 2001, Added 2001-10-22, Author Eric Giguere, Publisher Sun). Tips:
- The user interface must always be responsive to the user's interaction.
- The application should respond to input no later than a tenth of a second after it occurs: longer delays are noticed by the user, and make the user interface seem unresponsive. So don't do more than about a tenth of a second's worth of work in the user-service thread in response to any user interface event.
- Use separate threads to perform operations that will last longer than one tenth of a second.
- Provide the user with the option to cancel the operation at any time.
- [Article provides an example of making an HTTP connection following these suggestions].
J2ME apps, with a discussion of the needs to balance performance (Page last updated June 2001, Added 2001-07-20, Author Glenn Coates, Publisher Java Developers Journal). Tips:
- The application does not need to be lightning fast in order to have a responsive user interface. The perception of speed is important, for example, the user interface should give immediate feedback.
Creating Web-based, interactive graphics. (Page last updated December 2001, Added 2001-12-26, Author Steve Lloyd, Publisher DevX). Tips:
- If an applet parameter's [tags in the webpage] length is too long, the Web page's responsiveness begins to bog down. Move all but the essential parameters from the APPLET tag to a dedicated HTTP link between the applet and the servlet. This allows page loading and applet initialization to occur at the same time over separate connections.
Tuning tips intended for Sun's "Web Server" product, but actually generally applicable. (Page last updated 1999, Added 2000-10-23, Author ? - a Sun document, Publisher Aikido). Tips:
- Occasional very long GCs makes the VM hang for that time, leading to variability in service quality.
Improving applet download time by installing the applet on the client. (Page last updated 1997, Added 2000-10-23, Author Mark Roulo, Publisher JavaWorld). Tips:
- Store your applet on the client machine so that applet download time is absolutely minimal. This is not worth doing for really small applets.
Last Updated: 2021-03-29
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