Code review request: JDK-8005048,NMT: #loaded classes needs to just show the # defined classes

[Vitaly Davidovich]

David,

I suspect this is referring to the fact that InstanceKlass (VM
representation of java.lang.Class) can be in several states:
defined/allocated, loaded, linked/verified, etc.

Perhaps Classloader.define() and loadClass() are the classloader level
distinctions you're interested in?

Sent from my phone
On Dec 18, 2012 6:30 PM, "David Holmes" <david.holmes at oracle.com> wrote:

> On 19/12/2012 12:43 AM, Zhengyu Gu wrote:
>
>> Hi David,
>>
>> Thanks for reviewing.
>>
>> On 12/17/2012 9:41 PM, David Holmes wrote:
>>
>>> Hi Zhengyu,
>>>
>>> On 18/12/2012 6:11 AM, Zhengyu Gu wrote:
>>>
>>>> Current NMT implementation reports number of loaded classes at query
>>>> time, but number of defined classes is what is expected.
>>>>
>>>> This changset reflects two major changes:
>>>>
>>>> 1. It counts number of defined classes vs. number of loaded classes
>>>>
>>>
>>> Can you explain what the distinction is please? I don't know what a
>>> "defined class" is.
>>>
>>>  "defined class" refers to class definition (InstanceKlass), "loaded
>> class" refers to instance.
>>
>
> Sorry that didn't help. I don't understand what these two different things
> are (InstanceKlass vs. "instance" ???). Can you explain in terms of Java
> level class loading - when is a class "defined" versus "loaded"?
>
> Thanks,
> David
>
>
>>  2. It counts number of defined classes for each generation, vs. counts
>>>> at query time. In this way, the number of defined classes that NMT
>>>> reports, should match the corresponding class metadata data. As the
>>>> result, the data should be more accurate.
>>>>
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~**zgu/8005048/webrev.00/<http://cr.openjdk.java.net/~zgu/8005048/webrev.00/>
>>>>
>>>
>>> I think we could benefit from NMT_ONLY(x) macros to get rid of the
>>> one-line conditional blocks eg in instanceKlass.cpp
>>>
>> After consulting Chris Plummer, it does not have to exclude for
>> embedded. But yes, have NMT_ONLY() macros will be very helpful, I will
>> keep this in mind.
>>
>>
>>> ---
>>>
>>> src/share/vm/oops/**instanceKlass.hpp
>>>
>>> + #if INCLUDE_NMT
>>> + static int number_of_instance_classes() { return
>>> (int)_total_instanceKlass_**count; }
>>> +
>>> + private:
>>> + static volatile jint _total_instanceKlass_count;
>>> + #endif
>>>
>>> Why are we mixing int and jint here?
>>>
>> Yes, it is bad idea. Will change to "int"
>>
>> Thanks,
>>
>> -Zhengyu
>>
>>>
>>> ---
>>>
>>> I can't comment on the detailed memory management of the GenerationData.
>>>
>>> David
>>> -----
>>>
>>>
>>>
>>>> Thanks,
>>>>
>>>> -Zhengyu
>>>>
>>>