Proxy.isProxyClass scalability

[David Holmes]

Right - I was going to ask if those tools took into account injected fields.

David

On 26/01/2013 3:32 AM, Peter Levart wrote:
> Hi David,
>
> I think I already have a kind of answer. You wrote it in "RFR: 8005232
> (JEP-149) Class Instance size reduction":
>
> On 01/06/2013 11:46 PM, David Holmes wrote:
>> In Java 8, using a 32-bit example, a java.lang.Class instance is 112
>> bytes consisting of:
>>
>> - 8 byte object header
>> - 20 declared fields (mostly references, some int)
>> *- 5 injected fields (3 references, 2 ints) *
>>
>> That gives: 8 + (20*4) +(5*4) = 108 bytes. But as we need 8-byte
>> alignment that increases to 112 bytes.
>
> Regards, Peter
>
>
> On 01/25/2013 05:34 PM, Peter Levart wrote:
>> Hi David,
>>
>> I was surprised to see Usafe report these offsets. See below:
>>
>> 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*
>>
>>
>> Why the *24 bytes* gap between /classValueMap/ and
>> /classRedefinedCount/ fields?
>>
>> int classRedefinedCount *80*
>> int lastAnnotationsRedefinedCount 84
>>
>> java.lang.String *static* field offsets:
>>
>> Field Type Field Name Offset
>> ---------- ---------- ------
>> ObjectStreamField[] serialPersistentFields 96
>> Comparator CASE_INSENSITIVE_ORDER 100
>> long serialVersionUID 104
>> int HASHING_SEED 112
>>
>>
>> The 64 bit pointers variant:
>>
>> java.lang.Class instance field offsets:
>>
>> Field Type Field Name Offset
>> ---------- ---------- ------
>> Constructor cachedConstructor 16
>> Class newInstanceCallerCache 24
>> String name 32
>> SoftReference reflectionData 40
>> ClassRepository genericInfo 48
>> Object[] enumConstants 56
>> Map enumConstantDirectory 64
>> Map annotations 72
>> Map declaredAnnotations 80
>> AnnotationType annotationType 88
>> ClassValueMap classValueMap *96*
>>
>> *24 bytes* gap here too!
>>
>> int classRedefinedCount *128*
>> int lastAnnotationsRedefinedCount 132
>>
>> java.lang.String static field offsets:
>>
>> Field Type Field Name Offset
>> ---------- ---------- ------
>> ObjectStreamField[] serialPersistentFields 144
>> Comparator CASE_INSENSITIVE_ORDER 152
>> long serialVersionUID 160
>> int HASHING_SEED 168
>>
>>
>> Might it be that the "classRedefinedCount" field offset is fixed
>> somehow in VM, since the VM has to update it? Should there be VM
>> changes also to accomodate ReflectionData changes? Are there VM fields
>> inserted here that don't have a Java mapping?
>>
>> Regards, Peter
>>
>