[concurrency-interest] @Contended (JEP-142)

Kirk Pepperdine kirk at kodewerk.com
Fri Nov 30 09:20:01 EST 2012


I might add that the object ID information in OpenJDK in the binary format corresponds to address in heap and there is sizing information in there. If the padding is a regular field, it should show up as it would be the GC threads that are asked to perform the dump.. so the dump should contain what they would naturally see.

-- Kirk

On 2012-11-30, at 3:08 PM, Alan Bateman <Alan.Bateman at oracle.com> wrote:

> On 30/11/2012 13:36, Vitaly Davidovich wrote:
>> 
>> What's the plan for making this info available in heap dumps (taken using jmap)? I'd imagine tools like Eclipse MAT may want to indicate that a given instance of a class has padding applied.  Otherwise, the object size reported won't match expectation (without knowing that padding was applied).
>> 
> jmap triggers HotSpot to generate a heap dump in HPROF format, a format that is VM agnostic. The header allows for the word size but that's about it. This means that tools don't have the details on the actual layout, don't know about padding etc. from looking at the heap dump. It is an area that does need to be re-visited (for many reasons).
> 
> -Alan
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest at cs.oswego.edu
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest




More information about the Concurrency-interest mailing list