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

[Lois Foltan]

On 5/24/2018 5:25 PM, Thomas Stüfe wrote:

> Thanks for the review Lois!
>
> See comments inline.
>
> On Thu, May 24, 2018 at 10:31 PM, Lois Foltan <lois.foltan at oracle.com> 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.
> Sure - the majority of loaders seem not yet to have names, so this
> would remove a lot of "<unnamed>".
>
>> line #95 - would prefer <anonymous class> instead of just <anonymous>.
>> According to the comment at line #68, I think you intended that anyways.
>>
> Fixed.
>
>> Thanks,
>> Lois
>>
> New webrev:
>
> http://cr.openjdk.java.net/~stuefe/webrevs/8203455-VM.metaspace-display-loader-name-for-anonymous-cld/webrev.02/webrev/src/hotspot/share/memory/metaspace/printCLDMetaspaceInfoClosure.cpp.udiff.html

Thomas,
Looks good, thank you for making those changes!
Lois

>
> Example output:
>
> anonymous class, loader has name:
>    5: CLD 0x00007f814c47a7d0 for <anonymous class>, loaded by app
> instance of jdk.internal.loader.ClassLoaders$AppClassLoader
>
> anonymous class in <boot>
>    6: CLD 0x00007f814c474ae0 for <anonymous class>, loaded by <bootstrap>
>
> loader has name and class name:
>    7: CLD 0x00007f814c3afc60 for app instance of
> jdk.internal.loader.ClassLoaders$AppClassLoader
>
> <boot>:
>    8: CLD 0x00007f814c1d8570 for <bootstrap>
>
> Thank you,
>
> Thomas
>
>>> 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
>>