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

[David Holmes]

On 19/12/2012 11:05 AM, Vitaly Davidovich wrote:
> You sure define is last step? Even classloader javadoc says it still
> needs to be resolved (linked and verified, I presume).

Sorry I was being imprecise. After class definition the class is loaded 
but may still need to be resolved (linked).

A loaded Class at the Java level can be in one of three states:
- loaded, unlinked, uninitialized
- loaded, linked, uninitialized
- loaded, linked, initialized

Thanks,
David

> Sent from my phone
>
> On Dec 18, 2012 7:59 PM, "David Holmes" <david.holmes at oracle.com
> <mailto:david.holmes at oracle.com>> wrote:
>
>     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>
>         <mailto: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/>
>         <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
>