remove synthetic modules from modules cache to allow GC

[ben hockey]

the synthetic (require* + uid()) modules don't need to be cached. by deleting them from modules they can be garbage collected. by adding the following patch to finishExec in dojo.js, using chrome's profiling tools, i was able to observe the retained size for the modules cache drop from 1.2Mb to 400kb

dojo.js

@@ -1083 +1082 @@
                                        i++;
                                }
                        }
+                       // delete references to synthetic modules
+                       if (/^require\*/.test(module.mid)) {
+                               delete modules[module.mid];
+                       }
                },
 
                circleTrace = [],

it's possible that there's a better place to put these few lines and perhaps a better regular expression could be used but that was my best stab at it.

[ben hockey]

fyi - the results i mentioned were measured on an app i'm working on.

[Rawld Gill]

thanks neonstalwart; good point.

I think we need to look at some other places this kind of strategy can be followed as well (e.g., once a module is fully defined, the only thing that is really necessary to keep is the result).

[Rawld Gill]

In [28055]:

improved gc; thanks neonstalwart; refs #14909; !strict

[ben hockey]

Replying to rcgill:

I think we need to look at some other places this kind of strategy can be followed as well (e.g., once a module is fully defined, the only thing that is really necessary to keep is the result).

yes, there's probably more places to apply this. your example (only keeping the result for fully defined modules) set me off on a tangent thinking about what should happen when 2 module ids map to the same url - see ​https://groups.google.com/d/topic/amd-implement/E4ue9Q9Fimc/discussion for details.

btw, i'm updating some of the metadata for this ticket so it doesn't fall through the cracks but feel free to adjust as needed.

[Colin Snover]

1.8 is frozen. Move all enhancements to next release. If you need an exemption from the freeze for this ticket, contact me immediately.

[Rawld Gill]

This was fixed some time ago, but never marked as such.

[bill]

OK, so presumably in 1.9 or earlier.