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https://issues.apache.org/jira/browse/MNG-6311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16331697#comment-16331697
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David Churcher commented on MNG-6311:
-------------------------------------
Thanks Karl, there are 13 modules in this itest project, with 300-500 direct
and transitive dependencies per module. The tests take around 5 minutes in
total to run. It is running single-threaded (not using -T). Running from the
command line. File system is Windows NTFS on SSD. It is a default Java build. I
have sent a -X debug log and a dependency:tree log to your Github email
address. It's running on JDK8.
I ran it with the profiler extension, which shows that the time is nearly all
spent at the Project Discovery stage: 1196997 ms (20 minutes). With the
attached patch this falls to 1521 ms.
> Maven intolerably slow when import scope used heavily in large project
> ----------------------------------------------------------------------
>
> Key: MNG-6311
> URL: https://issues.apache.org/jira/browse/MNG-6311
> Project: Maven
> Issue Type: Bug
> Components: core, Performance
> Affects Versions: 3.5.0, 3.5.2
> Reporter: David Churcher
> Priority: Major
> Labels: performance
> Attachments: anon-hierarchy-maven-output.zip, modelcachefix.diff
>
>
> I have a build performance problem that is identical to MNG-5312, and has
> appeared since MNG-6030 in Maven v3.5.0 reversed the patch for MNG-5312,
> removing the ModelCache from some of the overloads for
> DefaultProjectBuilder.build.
> As in MNG-5312 the problem is in a large proprietary project. It uses up to 8
> levels of parent POMs, many of which use the import scope and have large
> dependency-management sections, and has hundreds of dependencies that also
> use the same parent POM hierarchy. Adding some logging shows that Maven does
> over 800,000 uncached reads of parent POM files, which takes about half an
> hour. With model caching this goes down to a few seconds.
> I've attached a patch that fixes this by using a class-level ModelCache in
> DefaultProjectBuilder. This does not suffer from the memory usage problems
> reported in MNG-6030.
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