Request for review:7133260:Remove -Xaprof and the usage of Klass:_alloc_count and ArrayKlass::_alloc_size

[Jiangli Zhou]

Hi Stefan,

Here is updated webrev with object_iterate_since_last_GC and 
with_array_klasses_do removed.

   http://cr.openjdk.java.net/~jiangli/7133260/webrev.01/

Thanks,
Jiangli

On 06/05/2013 09:44 AM, Jiangli Zhou wrote:
> Hi Stefan,
>
> On 06/05/2013 01:48 AM, Stefan Karlsson wrote:
>> On 06/05/2013 04:15 AM, Jiangli Zhou wrote:
>>> Hi,
>>>
>>> Please review following change for 7133260.
>>>
>>>   http://ccc.us.oracle.com/7133260
>>
>> I looked at:
>> http://cr.openjdk.java.net/~jiangli/7133260/webrev.00
>
> Thanks for doing that! Sorry for the wrong link.
>
>>
>> Looks good. Thanks for doing this cleanup.
>>
>> You remove the last usage of:
>>  object_iterate_since_last_GC
>>  with_array_klasses_do
>>
>> so there's even more cleanups that can be done here.
>
> That does appear to be the case. Thanks for noticing that. I'll try to 
> remove them as well.
>
>>
>>>
>>> In JDK8, -Xaprof support is outdated and broken. A new feature, 
>>> GC.class_stats command has been added to jcmd in JDK8. It provides 
>>> detailed class metadata memory statistics information. -Xaprof uses 
>>> Klass:_alloc_count and ArrayKlass::_alloc_size. Removing -Xaprof and 
>>> related fields would save 4bytes per class and 8bytes per array class.
>>
>> FTR, I don't think you save 8 bytes for the array classes. The size 
>> of ArrayKlass increased so that the vtable offset matches the vtable 
>> offset of the InstanceKlasses. See ArrayKlass::static_size.
>
> Thanks for pointing out the ArrayKlass::static_size. You are right, 
> the array class size is increased to be the same as InstanceKlass size 
> in ArrayKlass::static_size. I will fix CCC. So removing fields from 
> ArrayKlass does not yield real saving. :( It also means any size 
> reduction in InstanceKlass would help array class. :) Any reason why 
> ArrayKlass and InstanceKlass vtable offset need to be matched?
>
> Thanks for the review!
>
> Jiangli
>
>>
>> thanks
>> StefanK
>>
>>> Please see more information in the CCC request: 
>>> http://ccc.us.oracle.com/7133260.
>>>
>>> Tested with JPTR and vm.quick.testlist.
>>>
>>> Thanks,
>>> Jiangli
>>
>