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

[Thomas Stüfe]

On Mon, May 21, 2018 at 8:50 AM, David Holmes <david.holmes at oracle.com> wrote:
> On 21/05/2018 4:46 PM, Thomas Stüfe wrote:
>>
>> Hi David,
>>
>> On Mon, May 21, 2018 at 4:23 AM, David Holmes <david.holmes at oracle.com>
>> wrote:
>>>
>>> Hi Thomas,
>>>
>>> There's been a bit of discussion lately about how to "describe"
>>> classloaders:
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8202605
>>>
>>> I'd rather not see another chunk of code added that 8202605 will have to
>>> fix
>>> up. Can you live with the less-than-ideal output of the existing
>>> function,
>>> under the expectation it will be updated to do a better job in the
>>> future?
>>>
>>
>> 8206205 does not alleviate the need for this change, since currently
>> we do not print any loader information for anonymous classes.
>
>
> Sorry I was unclear. I meant for this patch to just add e.g. use of
> loader_name(), even if not ideal, and allow 8202605 to clean up the actual
> text later.
>

Ah, okay. Lets see how discussion under 8202605 goes - I just added a
comment. I really want to print out loader name *and* class name, not
one or the other.

Thomas

> David
>
>> Originally I planned to fix up this patch with a follow up patch later
>> once those utility functions are in place in ClassloaderData.
>>
>> But yes, I can save us some review work by waiting a bit and then
>> doing only one change. Lets hope it does not take too long, I have
>> more changes coming up which print class loader names.
>>
>> So I retract this RFR for now and will repost another patch once
>> 8206205 is done.
>>
>> Thanks, Thomas
>>
>>> Thanks,
>>> David
>>>
>>>
>>> On 20/05/2018 4:49 PM, Thomas Stüfe 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
>>>>
>>>
>