In 32 bit Server,what's the size of Java.Lang.Object

[Krystal Mok]

Yes, Vitaly is right. That presentation described the situation in IBM's J9
VM, which is different from Oracle JDK/OpenJDK's HotSpot VM. J9 uses a
dedicated word for locks, where as HotSpot folds that into the mark word.

So an object with no explicit fields in a 32-bit HotSpot VM uses 8 bytes, 4
for the mark word and 4 for the klass pointer.

- Kris

On Fri, Oct 19, 2012 at 9:27 PM, Vitaly Davidovich <vitalyd at gmail.com>wrote:

> The presentation may be talking about IBM's VM.  Hotspot obj header is two
> words; arrays have an extra int32 for length.
>
> Sent from my phone
> On Oct 19, 2012 9:15 AM, "fuyou" <fuyou001 at gmail.com> wrote:
>
>> hi all
>>       I am issues about in 32 bit Server,what's the size of
>> Java.Lang.Object
>> in this blog how-much-memory-is-used-by-my-java<http://kohlerm.blogspot.com/2008/12/how-much-memory-is-used-by-my-java.html>
>>   java.lang.Object: 2 * 4 (Object header),the size of Object is 2*4
>> but in the sessioCON5135_PDF_5135_0001.pdf<http://www.myexpospace.com/JavaOne2012/SessionFiles/CON5135_PDF_5135_0001.pdf> (page
>> 9)   Object Metadata: 3 slots of data (4 for arrays, Class: pointer to
>> class information,Flags: shape, hash code, etc, Lock: flatlock or pointer
>> to inflated monito)
>>  so the size of Object is 3*4
>>
>> who is right?
>>
>> --
>>    =============================================
>>
>>     fuyou001
>> Best Regards
>>
>>
>>
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