[GitHub] [maven] gnodet commented on issue #259: [MNG-6693] Various speed improvements

[GitBox <gi...@apache.org>]

gnodet commented on issue #259: [MNG-6693] Various speed improvements
URL: https://github.com/apache/maven/pull/259#issuecomment-506768131
 
 
   How ? You mean why each change helps improving performance or how did I measure the effect ? or how did i find those ?
   For the _what_, my main goal is to speed up `time mvn foo` when running the build on https://github.com/apache/camel, so that's easily reproducible.  Currently, with 3.6.1, it takes more than 50s.  I'm now slightly above 30s with all the included changes.
   As for the _how_, I'm using YourKit profile to find out the spots that takes times.  I've been spending a lot of time trying to improve the model building mechanism in various ways, but could not get any significant results, so I'm back to a bunch of smaller improvements, which is the subject of this PR.
   For the specifics, it depends:
     - using regexp is quite slow for simple checks, so checking if there's a '-' in a string is *way* faster than running the regexp in the first place, so if we can avoid it, it's better
     - avoid running the full model interpolation on the parent if the version is not to be interpolated
     - speed up the string search interpolator by reusing the plexus interpolator instead of adding / removing the same value sources / processors each time
     - cache valid ids (they are mostly always the same)
     - avoid concatenating strings which are not used (during validation, as they are only used when there's a violation)
     - the second commit provides a full blown new model interpolator which does not use reflection and is much master
     - the third commit does early checking before calling `Validate.notBlank` which proves to be quite slow when called a few million times
   

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