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

[Lois Foltan]

On 5/21/2018 3:42 AM, Thomas Stüfe wrote:

> 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.

Hi Thomas,

Looks good, thanks for using ClassLoaderData::class_loader_name()! A 
couple of review comments:

- src/hotspot/share/memory/metaspace/printCLDMetaspaceInfoClosure.cpp
line #82 - I do not prefer the use of "<unnamed>", but am more in favor 
of leaving it out and having the message simply read "CLD for instance 
of <loader class name>".  Please consider.
line #95 - would prefer <anonymous class> instead of just <anonymous>.  
According to the comment at line #68, I think you intended that anyways.

Thanks,
Lois

>
> 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