RFR (M): 8207266: ThreadMXBean::getThreadAllocatedBytes() can be quicker for self thread

[David Holmes]

On 19/09/2019 12:57 pm, Mandy Chung wrote:
> On 9/18/19 5:00 PM, Hohensee, Paul wrote:
>> They all implement com.sun.management.ThreadMXBean, so adding a 
>> getCurrentThreadAllocatedBytes broke them. Potential fix is to give it 
>> a default implementation, vis
>>
>>      public default long getCurrentThreadAllocatedBytes() {
>>          return -1;
>>      }
>>
> 
> com.sun.management.ThreadMXBean (and other platform MXBeans) is a 
> "sealed" interface which should only be implemented by JDK. 

Didn't realize that. I don't recall knowing about PlatformManagedObject. 
Sealed types will at least allow this to be enforced, though I have to 
wonder what the tests are doing here.

> Unfortunately we don't have the sealed type feature yet.  Yes it needs 
> to be a default method.  I think it should throw UOE.
> 
>       * @implSpec
>       * The default implementation throws {@code 
> UnsupportedOperationException}.
> 
> The @throw UOE can make it clear that it does not support current thread 
> memory allocation measurement.

Yes that seems a reasonable default if we don't want this to be 
implemented outside the platform.

Thanks,
David

> Mandy