Nglayout.debug.disable xul fastload
Background
To improve performance, Mozilla saves a “compiled” version of the XUL and JavaScript to disk periodically so that it does not have to re-parse the data from chrome files on startup. This caching (often referred to as “XUL FastLoad” or just “FastLoad”) significantly decreases the time it takes to do a cold start of a Mozilla application.
The file to which the serialized data is saved differs by platform. On OS X it’s XUL FastLoad File; on Linux it’s xul.mfasl; and on Windows it’s XUL.mfl.
Possible values and their effects
True
Do not save serialized XUL/JS to disk.
False
Save serialized versions of parsed XUL/JS to disk for faster startup times. (Default)
Caveats
- There is (unsurprisingly) a performance hit associated with setting this preference to true.
- XUL FastLoad works without the XUL cache on, but FastLoad’s effects will be limited to JavaScript.
- Conversely, the XUL cache works without FastLoad, but the cache will not be saved between Mozilla sessions.
Previous effects
Until mid-2002, FastLoad (and thus this preference) was only concerned with the serialization of JavaScript. FastLoad began serializing XUL documents after bug 112064 was fixed.
First checked in
Has an effect in
- Mozilla Suite (all versions since 0.9.4)
- Mozilla Firefox (all versions)
- Mozilla Thunderbird (all versions)
- SeaMonkey (all versions)
Related bugs
- Bug 68045 - precompile chrome JS and load it incrementally ("fastload")
- Bug 112064 - Fastload XUL documents and elements