RFR 8231146: Heap object size

[Mandy Chung]

JOL seems to hard code the oop size as a pointer size in certain 
implementation of DataModel?

I believe JVM TI GetObjectSize and Instrumentation::getObjectSize 
already support inline classes.  It'd good to verify.

Mandy

On 9/20/19 9:38 AM, Roger Riggs wrote:
> Yes, JOL will need an update. It thinks all object fields size is just 
> a reference (4).
> I included an inline class Point(int x, int y)...
>
> Regards, Roger
>
> M Layout Simulation 
> (org.openjdk.jol.datamodel.CurrentDataModel at 433f4e98, field allocation 
> style: 2)
> Class150176 object internals:
>  OFFSET  SIZE                         TYPE 
> DESCRIPTION                               VALUE
>       0    12                              (object 
> header)                           N/A
>      12     4                              (alignment/padding gap)
>      16     8                         long 
> Class150175.field1                        N/A
>      24     2                        short 
> Class150175.field2                        N/A
>      26     1                         byte 
> Class150175.field3                        N/A
>      27     1                              (alignment/padding gap)
>      28     4             java.lang.Object 
> Class150175.field0                        N/A
>      32     4   org.openjdk.jol.util.Point 
> Class150176.field1                        N/A
>      36     4   org.openjdk.jol.util.Point 
> Class150176.field3                        N/A
>      40     8                       double 
> Class150176.field2                        N/A
>      48     2                        short 
> Class150176.field0                        N/A
>      50     6                              (loss due to the next 
> object alignment)
> Instance size: 56 bytes
> Space losses: 5 bytes internal + 6 bytes external = 11 bytes total
>
>
>
> On 9/20/19 9:03 AM, Roger Riggs wrote:
>> Hi Aleksey,
>>
>> I'll have to try it, but I don't expect it to be able to understand 
>> the embedding
>> in objects or arrays without an update.
>>
>> This is for exploratory work on using inline classes and algorthms.
>>
>> JOL is not in an API in java.base that can be used to dynamically adjust
>> data structures based on actual embedding.
>>
>> I expect any long term APIs to be different and more detailed.
>>
>> Thanks, Roger
>>
>>
>> On 9/20/19 8:47 AM, Aleksey Shipilev wrote:
>>> On 9/17/19 10:00 PM, Roger Riggs wrote:
>>>> In prototyping with inline classes it will be useful to know an 
>>>> approximation of the size of an
>>>> object in the heap while prototyping various tradoffs in 
>>>> performance and data structures.
>>> Any reason why JOL does not work?
>>>    http://openjdk.java.net/projects/code-tools/jol/
>>>
>>> It already calls through the existing interfaces to figure out the 
>>> object size.
>>>
>>
>