Request for review: 8003848: Make ConstMethod::generic_signature_index optional and move Method::_max_stack to ConstMethod

[Coleen Phillimore]

Hi Jiangli,

On 11/27/2012 11:06 AM, Jiangli Zhou wrote:
> Hi Coleen,
>
> I remember now you suggested moving those fields as well when I 
> proposed the change. I'll move max_locals and size_of_parameters into 
> constMethod. Would it be okay if I push this as is and work on the 
> other two fields on the same time?

Sure, that is fine.  Can you file a bug for it?  I don't think there is 
one yet.
Thanks,
Coleen

>
> Thanks!
> Jiangli
>
> On 11/26/2012 07:35 PM, Coleen Phillimore wrote:
>>
>> Jiangli,
>>
>> This code looks fine, although I don't like that max_stack is being 
>> moved without moving max_locals.   They're usually used together in 
>> the same place.   If you moved max_locals and size_of_parameters also 
>> with this change into constMethod, I think it would be better.   
>> Also, we want to move these fields anyway for more sharing with CDS.
>>
>> Thanks,
>> Coleen
>>
>> On 11/26/2012 9:08 PM, serguei.spitsyn at oracle.com wrote:
>>> Jiangli,
>>>
>>> It looks good.
>>>
>>> Thanks,
>>> Serguei
>>>
>>> On 11/21/12 11:53 AM, Jiangli Zhou wrote:
>>>> Hi,
>>>>
>>>> Please review the following memory reduction change for Method and 
>>>> ConstMethod:
>>>>
>>>>   http://cr.openjdk.java.net/~jiangli/8003848/webrev/
>>>>
>>>> Majority of java methods do not have generic signature. For those 
>>>> methods, ConstMethod::generic_signature_index are always 0. 
>>>> ConstMethod::generic_signature_index can be optional and only 
>>>> allocated for methods with generic signature.
>>>>
>>>> The Method class has 2-byte unused due to padding for alignment. 
>>>> Method::_max_stack can be moved to ConstMethod after changing 
>>>> ConstMethod::generic_signature_index to be optionally allocated. 
>>>> This removes an u2 field in Method, and can avoid the 2-byte unused 
>>>> space waste due to padding.
>>>>
>>>> Together, above would save 4-bytes for each java method without 
>>>> generic signature.
>>>>
>>>> Tested with jprt, runthese and vm.quick.testlist. No measurable 
>>>> performance difference with the change for specjvm98 and specjbb2005.
>>>>
>>>> ============================================================================== 
>>>>
>>>> logs.method_baseline.jbb:
>>>>   Benchmark           Samples        Mean     Stdev Geomean Weight
>>>>   specjbb2005               3    56252.53    284.79
>>>> ============================================================================== 
>>>>
>>>> logs.method.jbb.1:
>>>>   Benchmark           Samples        Mean     Stdev   %Diff P 
>>>> Significant
>>>>   specjbb2005               3    56350.15    626.79    0.17 
>>>> 0.823            *
>>>> ============================================================================== 
>>>>
>>>>
>>>> ============================================================================== 
>>>>
>>>> logs.method_baseline.spec:
>>>>   Benchmark           Samples        Mean     Stdev Geomean Weight
>>>>   specjvm98                 8      543.39     11.93
>>>> ============================================================================== 
>>>>
>>>> logs.method.spec.1:
>>>>   Benchmark           Samples        Mean     Stdev   %Diff P 
>>>> Significant
>>>>   specjvm98                 8      544.21      9.56    0.15 
>>>> 0.881            *
>>>> ============================================================================== 
>>>>
>>>>
>>>>
>>>> Thanks,
>>>> Jiangli
>>>
>>
>