Request for review: 8004076: Move _max_locals and _size_of_parameters to ConstMethod for better sharing

[Jiangli Zhou]

Hi John,

Thanks a lot for looking at the change again and the field compressing 
suggestion! I've looked into the FieldInfo array and optimized the 
memory usage for the generic signature index slot earlier this year. I 
haven't played with any compression technique. Thanks for the 
suggestion, definitely worth to look into. I have one question maybe you 
have quick answer to it. Does C1 or C2 heavily relying on fast accessing 
to the FieldInfo array?

Thanks,

Jiangli

On 12/10/2012 03:10 PM, John Rose wrote:
> On Dec 9, 2012, at 9:53 PM, Jiangli Zhou wrote:
>
>> Hi John,
>>
>> Here is the updated webrev with Address constant change in where it's 
>> appropriate:
>>
>> http://cr.openjdk.java.net/~jiangli/8004076/webrev.01/.
>>
>> I'm also double checking with jprt and runthese tests.
>
> Yes, that's much nicer; thanks.
>
> Has your group been considering compressing the field metadata 
> (type FieldInfo)?
>
> I think that, by using a variable-length byte-oriented format, we 
> could easily cut the size of that data by more than 50%.
>
> The initval field and the high part of the offset are almost always 
> zero.  The number of access flags configurations is very small, much 
> smaller than 2**16.  (Low entropy everywhere!)  All this means they 
> could be profitably cut out most of the time with profit, as long as 
> the access method does not slow the VM down detectably.
>
> I'm thinking about this because of Alexey's work on @Contended and the 
> upcoming work on @Stable.  Also, if we do field profiling we may need 
> to add miscellaneous bits to the field metadata.
>
> — John

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