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

[David Holmes]

On 19/12/2012 10:54 AM, Vitaly Davidovich wrote:
> 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.

Okay. It would be good to be clear on that.

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

define() is the final step of loadClass(): first find the bytes for the 
class then send them to the VM via defineClass to actually load the 
class. "define" is not a state at the Java level.

Thanks,
David

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