RFR 8231146: Heap object size

[Roger Riggs]

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.
>>
>