Proxy.isProxyClass scalability

[Peter Levart]

On 01/25/2013 05:42 PM, Aleksey Shipilev wrote:
> On 01/25/2013 08:37 PM, Peter Levart wrote:
>> On 01/25/2013 05:34 PM, Aleksey Shipilev wrote:
>>>        80     4   ClassValueMap Class.classValueMap
>>>        84    12                 (alignment/padding gap)
>> What's this? why 12 bytes?
>>>        96     4             int Class.classRedefinedCount
> Beats me, some voodoo VM magic? This is what Unsafe reports anyway. Your
> data have the same gap (though not immediately evident because you don't
> calculate the offset differences).
>
> -Aleksey.
j.l.Class seems to be very special with it's own layout lo(ma)gic. For 
example, I copied the source of j.l.Class into j.l.MyClass and 
chopped-out all the methods, which gives the following (32 bit pointers):

java.lang.MyClass instance field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
*                     int classRedefinedCount     12**
**                     int lastAnnotationsRedefinedCount     16*
              Constructor cachedConstructor     20
                    Class newInstanceCallerCache     24
                   String name     28
            SoftReference reflectionData     32
          ClassRepository genericInfo     36
                 Object[] enumConstants     40
                      Map enumConstantDirectory     44
                      Map annotations     48
                      Map declaredAnnotations     52
           AnnotationType annotationType     56
            ClassValueMap classValueMap     60

the primitive fields come before pointers whereas in j.l.Class:

java.lang.Class instance field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
              Constructor cachedConstructor     12
                    Class newInstanceCallerCache     16
                   String name     20
            SoftReference reflectionData     24
          ClassRepository genericInfo     28
                 Object[] enumConstants     32
                      Map enumConstantDirectory     36
                      Map annotations     40
                      Map declaredAnnotations     44
           AnnotationType annotationType     48
            ClassValueMap classValueMap     52
*                     int classRedefinedCount     80**
**                     int lastAnnotationsRedefinedCount     84*

...they come after the pointers and the first one has a strange alignment...


Regards, Peter