RFR(M): 8017317: PPC64 (part 7): cppInterpreter: implement support for biased locking

[Vladimir Kozlov]

David,

Do you insist on moving cppInterpreter files into separate directory? If 
yes, we need to do that in our main sources to avoid merges nightmare. 
And I will do the move.

Thanks,
Vladimir

On 6/27/13 5:18 AM, David Holmes wrote:
> Vladimir,
>
> On 27/06/2013 9:34 AM, Vladimir Kozlov wrote:
>> Hi Goetz,
>>
>> On 6/26/13 7:30 AM, Lindenmaier, Goetz wrote:
>>> Hi,
>>>
>>> To use biased locking in our PPC64 VM,we fixed the biased locking
>>> implementation
>>> in the cppInterpreter.  We also added  BiasedLockingStatistic support.
>>
>> Oracle does not use cppInterpreter and no building and testing are done.
>> So we trust you to do testing of these changes.
>> I glanced on these changes and they look fine to me.
>>
>> One suggestion I heard from David H. is to move cppInterpreter related
>> files (all 6 of them) from interpreter/ directory to separate directory.
>> So we can see when changes does not affect our shared code.
>
> It is a general source of confusion to new hotspot engineers that there
> are actually two interpreters in one directory and that one is not used
> by the historical primary ports. It also isn't obvious that
> bytecodeInterpreter.cpp pertains to the cppInterpreter.
>
>>> We need an additional ordering operation in revoke_bias() when writing
>>> the mark.
>>
>> Why you need ordering only for locked objects in this code? And why here
>> at all? This code is executed at safepoint.
>
> There is one occurrence that is not executed at a safepoint - see
> BiasedLocking::Condition BiasedLocking::revoke_and_rebias. Though it
> seems to be operating only on current thread in that case.
>
> The use of release_set_mark seems consistent with other uses in
> synchronizer.cpp.
>
> David
> -----
>
>> thanks,
>> Vladimir
>>
>>> The change enables biased locking for ppc64 per default.
>>> http://cr.openjdk.java.net/~goetz/webrevs/8017317-lock/
>>>
>>> Please review and test this change.
>>>
>>> Best regards,
>>>    Goetz
>>>