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From Jonathan Haber <jha...@hubspot.com>
Subject Re: Summary of meeting about Maven performance improvements
Date Wed, 24 Apr 2019 11:29:29 GMT
>
> We need to find out who is interested in these kind improvements inside
> the Maven community.


Just wanted to throw my two cents in. My company is a relatively large
Maven user and we're very interested in these sorts of improvements. We've
tried to upstream improvements in the past, but have been a bit discouraged
by patches/PRs stagnating. So we mostly end up forking plugins and using
those forks internally, which is a shame because no one else in the Maven
community gets to benefit. It sounds like this customer did something
similar with their performance improvements. So you have Maven users who
are ready, willing, and able to contribute improvements but get defeated by
the process, which is a shame. Obviously the Maven team has finite
resources so I'm not suggesting that there's a trivial answer.

On Wed, Apr 24, 2019 at 4:51 AM Benedikt Ritter <britter@apache.org> wrote:

> Hello,
>
> this is a summary of a video conference call that happened yesterday (April
> 24).
>
> Topic:
> Discussion about performance improvements that have been proposed by Stefan
> Oehme, namely:
>
> - [MNG-6638] - Prevent reparsing POMs in MavenMetadataSource (
> https://github.com/apache/maven/pull/244)
> <https://github.com/apache/maven/pull/244)>
> - [MNG-6633] - Reduce memory usage of excludes (
> https://github.com/apache/maven/pull/243)
> <https://github.com/apache/maven/pull/243)>
> - Speed up project discovery (
> https://github.com/apache/maven/pull/242)
> <https://github.com/apache/maven/pull/242)>
> - Make location handling more
> memory efficient (https://github.com/codehaus-plexus/modello/pull/31
> <https://github.com/codehaus-plexus/modello/pull/31>
> )
>
> The goal of this call was to give some more insights into how Stefan found
> the improvements and to better understand what is missing before these
> changes be merged.
>
> Attendees of the call:
> - Benedikt Ritter (Gradle Inc.)
> - Stefan Oehme (Gradle Inc.)
> - Robert Scholte (Apache Maven Team)
> - Hervé Boutemy (Apache Maven Team; joined about half an hour after the
> call started)
>
> Summary:
>
> Stefan gave some insights into how he discovered bottlenecks in Maven:
>
> -
>
> One of our customers has a huge Maven build:
> -
>
> Lots of sub projects (2000)
> -
>
> Lots of entries in dependency management (4000)
> -
>
> Results in a lot of garbage collection
> -
>
> Problems discovered in that build:
> -
>
> Re-parsing project POMs during dependency resolution
> -
>
> Model objects are too large because of location tracking
> -
>
> Low-level bottlenecks in project discovery (especially version
> parsing)
> -
>
> Customer now has a Maven fork with the proposed changes included:
> -
>
> 1h 50min, 12GB RAM without changes
> -
>
> 45min, 8GB RAM with changes
>
>
> Robert:
>
> -
>
> How to ensure that improvements are not broken?
> -
>
> No answer to how to test this
>
>
> Stefan gave some insights into how performance testing works in the Gradle
> project:
>
> -
>
> Build has a project generator
> -
>
> Create different projects in different shapes (e.g. lots of subprojects,
> deeply nested projects) during the build
> -
>
> Download old Gradle version and run the build on generated projects
> -
>
> Run build again with current Gradle version
> -
>
> Compare results
> -
>
> use statistic methods to filter out variance
> -
>
> Downside to this approach is that it requires a lot of computing
> resources
>
> More information can be found on GitHub:
> https://github.com/gradle/gradle/tree/master/subprojects/performance
> <https://github.com/gradle/gradle/tree/master/subprojects/performance>
> The corresponding TeamCity build can be found here:
>
> https://builds.gradle.org/viewLog.html?buildId=22179604&buildTypeId=Gradle_Check_PerformanceExperimentCoordinator&tab=report_project941_Performance&branch_Gradle_Check_Stage_ReadyforRelease=master
> <https://builds.gradle.org/viewLog.html?buildId=22179604&buildTypeId=Gradle_Check_PerformanceExperimentCoordinator&tab=report_project941_Performance&branch_Gradle_Check_Stage_ReadyforRelease=master>
> (use
> "Login as guest" to view)
>
> Robert:
>
> -
>
> What about measuring performance using instruction calls?
>
>
> Stefan:
>
> -
>
> The performance improvements we found were mostly about garbage being
> created
> -
>
> Measuring using instruction calls is interesting
> -
>
> ... but it is also very machine dependent
>
>
> Robert:
>
> -
>
> We need to find out who is interested in these kind improvements inside
> the Maven community.
> -
>
> Build a community of people who would like to work on these kind of
> things.
>
>
> Stefan:
>
> -
>
> It's easy to get started. We just used open source tools:
> -
>
> We used async-profiler for measuring things (
> https://github.com/jvm-profiling-tools/async-profiler
> <https://github.com/jvm-profiling-tools/async-profiler>
> )
> -
>
> Heap dumps for analyzing memory usage
>
> To get started with performance tests in the maven project:
>
> -
>
> Start with only a few test projects
> -
>
> The Gradle generator is Apache License v2 and can be used as a starting
> point to generate a big maven project
>
>
> Hervé:
>
> -
>
> PRs should be merged soon
> -
>
> Discussion need to be resolved
> -
>
> Why was the PR not merged after the discussion and resolving all issues
> with the code?
> -
>
> Hervé will take care that the changes are merged soon
>
>
> Thank you!
> Benedikt
>

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