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

[David Holmes]

Hi Lois,

On 25/05/2018 6:31 AM, Lois Foltan wrote:
> 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.

I thought this style had already been put in place:

open/src/hotspot > grepsrc.sh "<unnamed>"
./share/classfile/javaClasses.cpp:    name = "<unnamed>";
./share/classfile/javaClasses.cpp:        parentName = "<unnamed>";
./share/classfile/javaClasses.hpp:  // If a classloader has no name, it 
prints <unnamed> instead. The output

??

> line #95 - would prefer <anonymous class> instead of just <anonymous>. 

"VM anonymous class"? (As opposed to Java language anonymous class.)

Thanks,
David

> 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
>