RFR(xs): 8203455: jcmd: VM.metaspace: print loader name for anonymous CLDs.

[Thomas Stüfe]

Hi all,

second attempt, after discussing things with David:

http://cr.openjdk.java.net/~stuefe/webrevs/8203455-VM.metaspace-display-loader-name-for-anonymous-cld/webrev.01/webrev/

The patch is much simpler now. I use
ClassLoaderData::class_loader_name() and ::class_loader_class() which
should always work and be in accordance with planned work in
https://bugs.openjdk.java.net/browse/JDK-8202605.

Thanks, Thomas


On Sun, May 20, 2018 at 8:49 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> Hi all,
>
> may I please have reviews for this small addition.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8203455
> Webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8203455-VM.metaspace-display-loader-name-for-anonymous-cld/webrev.00/webrev/
>
> VM.metaspace show-loaders can be used to display loaders (well, really
> CLD instances).
>
> For anonymous CLDs, only "anonymous" is shown. It would be helpful to
> show to which loader these CLD are assigned.
>
> Before:
>
>  "272: ClassLoaderData 0x00007f5ba0538f10 for anonymous class"
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8203455-VM.metaspace-display-loader-name-for-anonymous-cld/example-before.txt
>
> After patch:
>
>  "268: CLD 0x00007ff0c45738f0 for <anonymous class>, loaded by app,
> instance of jdk.internal.loader.ClassLoaders$AppClassLoader"
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8203455-VM.metaspace-display-loader-name-for-anonymous-cld/example-after.txt
>
> --
> Notes: this patch has a bit more lines than I liked because I did not
> find a singly utility function in ClassloaderData which fit my
> purpose. I wanted to see name and class of the associated loader for
> both normal and unloading case. ClassloaderData::loader_name() has a
> number of shortcomings, I opened
> https://bugs.openjdk.java.net/browse/JDK-8203456 as a follow up rfe.
>
> Thank you,
>
> Thomas