Request for review:7133260:Remove -Xaprof and the usage of Klass:_alloc_count and ArrayKlass::_alloc_size
jiangli.zhou at oracle.com
Wed Jun 5 09:44:23 PDT 2013
On 06/05/2013 01:48 AM, Stefan Karlsson wrote:
> On 06/05/2013 04:15 AM, Jiangli Zhou wrote:
>> Please review following change for 7133260.
> I looked at:
Thanks for doing that! Sorry for the wrong link.
> Looks good. Thanks for doing this cleanup.
> You remove the last usage of:
> 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 In JDK8, -Xaprof support is outdated and broken.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!
>> Please see more information in the CCC request:
>> Tested with JPTR and vm.quick.testlist.
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