RFR(s): jcmd VM.classloaders should fold similar loaders

[Thomas Stüfe]

Resent with the correct subject, sorry.

..Thomas

On Fri, Jun 22, 2018 at 9:08 PM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> Hi all,
>
> may I have reviews for this small enhancement to the jcmd
> VM.classloader diagnostic command:
>
> https://bugs.openjdk.java.net/browse/JDK-8205531
> http://cr.openjdk.java.net/~stuefe/webrevs/8205531-vm.classloader-tree-folding/webrev.00/webrev/
>
>
> VM.classloaders prints a tree of class loaders. This tree can grow a
> lot and become unwieldy, especially with a lot of similar loaders. One
> prime example is the DelegatingClassLoader. It would be helpful were
> all these loaders:
>
> 13114:
> +-- <bootstrap>
>       |
>       +-- "platform", jdk.internal.loader.ClassLoaders$PlatformClassLoader
>             |
>             +-- "app", jdk.internal.loader.ClassLoaders$AppClassLoader
>                   |
>                   +-- test3.internals.InMemoryClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
>                         |
>                         ...... repeat 1495 times
>
>  folded into one:
>
> 13114:
> +-- <bootstrap>
>       |
>       +-- "platform", jdk.internal.loader.ClassLoaders$PlatformClassLoader
>             |
>             +-- "app", jdk.internal.loader.ClassLoaders$AppClassLoader
>                   |
>                   +-- test3.internals.InMemoryClassLoader
>                         |
>                         +-- jdk.internal.reflect.DelegatingClassLoader
> (+ 1499 more)
>
>
> Original idea by Bernd Eckenfels, see
> http://mail.openjdk.java.net/pipermail/serviceability-dev/2018-May/023824.html
>
> Thank you, Thomas