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Improving Nasal: Difference between revisions
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Also see: [[How the Nasal GC works]] | Also see: [[How the Nasal GC works]] | ||
Year: 2011 | Year: 2011-2012 | ||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg33190.html | URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg33190.html | ||
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blocking may occur. Frame rate may also influce it: many Nasal timers | blocking may occur. Frame rate may also influce it: many Nasal timers | ||
run at delay 0 (in every update loop). | run at delay 0 (in every update loop). | ||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37308.htmla | |||
A significant part of Nasal-related frame rate impact is | |||
caused by garbage collection. Its delay/jitter only depends on the | |||
number of Nasal objects and their references which need to be searched. | |||
Increasing the number of Nasal objects (code+data) existing in memory | |||
also increases the delay. | |||
The amount of Nasal code which is actually being executed only | |||
influences the g/c frequency, i.e. whether the effect is visible every | |||
few seconds vs several times per second. | |||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37310.html | |||
I did look at incremental GC for Nasal last year, but couldn't find a 'simple | |||
enough' generational algorithm. Still happy for someone else to try - the Nasal | |||
GC interface is very clean and self-contained, so quite easy to experiment with | |||
different GC schemes. | |||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37338.html | |||
But as I said, I think really the GC needs to be addressed. There's only so | |||
much hacking around the actual problem one can do. | |||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37338.html | |||
Right, a problem is that I've possibly studied all Nasal documentation I could | |||
get without finding any reference of the GC problem - that was only transmitted | |||
to me much later. I think you'll find that most Nasal users are not aware of | |||
any such problems, because it's not documented anywhere. It doesn't help so | |||
much if you are aware of it. | |||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37338.html | |||
the current GC is bad, and big Nasal shows this while small Nasal doesn't. | |||
URL: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg37338.html | |||
We have an implementation of Nasal which dumps all the GC into a single frame | |||
and is apparently sensitive to the total amount of code, regardless if the code | |||
is actually run or not. This fact has historically not been widely advertized | |||
or explained. That turns out to be a problem. | |||
The way this usually comes across is 'Advanced Weather causes stutter'. But it | |||
actually doesn't really (or at least that remains to be shown) - what causes | |||
stutter is mainly the GC, and Advanced Weather just happens to trigger this. | |||
The range of suggested solutions in the past included almost everything, from | |||
avoiding Nasal to porting code to Nasal to hacking around the problem to | |||
loading things on-demand - except fixing the actual cause of the problems. | |||
I don't honestly know how complex code to collect garbage across many frames | |||
is, but somehow I doubt that in terms of man-hours the effort beats porting the | |||
existing large-scale Nasal codes to C++. Just my 2 cents in any case. | |||
== Separate GC implementations == | == Separate GC implementations == | ||