RFR(S) 8240244 Avoid calling resolve_super_or_fail in SystemDictionary::load_shared_class

[Lois Foltan]

On 3/3/2020 12:09 PM, Ioi Lam wrote:
>
>
> On 3/3/20 8:49 AM, Lois Foltan wrote:
>> On 3/3/2020 1:34 AM, Ioi Lam wrote:
>>> https://bugs.openjdk.java.net/browse/JDK-8240244
>>> http://cr.openjdk.java.net/~iklam/jdk15/8240244-reduce-resolve-super.v01/ 
>>>
>>>
>>> When loading shared classes from the CDS archive, we need to test if 
>>> the
>>> actually loaded super types are the same as those used during CDS 
>>> dumping.
>>> That was done with a pretty expensive call to resolve_super_or_fail.
>>>
>>> In most cases, the super type has already been loaded (about 350 out 
>>> of 400
>>> cases when running HelloWorld), so we can quickly determine that by
>>> doing a look up in the super type's dictionary.
>>>
>>> This saves about 250,000 out of about 112M instructions (about 
>>> 0.22%) when
>>> running HelloWorld with the default archive on Linux/x64.
>>>
>>> I also renamed a few functions in instanceKlass.hpp to 
>>> _xxx_shared_xxx since
>>> they are used only for CDS.
>>>
>>> Thanks
>>> - Ioi
>>>
>>>
>> Hi Ioi,
>>
>> Looks good, I like the move to consolidate the calls to resolve_super 
>> or fail into SystemDictionary::check_shared_class_super_type().  I 
>> have a minor comment about checking the loader against NULL.
>>
>> classfile/systemDictionary.cpp line #1266 & #1272, please consider 
>> using ClassLoaderData::is_the_boot_class_loader_data()
>>
>
> Hi Lois,
>
> Thanks for the review.
>
> The intention of the code is to read loader_data->dictionary() only if 
> InstanceKlass::class_loader_data() is not NULL.
>
> If a class X has been loaded by the boot class loader, 
> X->class_loader_data()  is non-null. It's only X->class_loader() that 
> is NULL.

Ahhh, thanks for the clarification.  I'm good with the changes!
Lois

>
> Thanks
> - Ioi
>
>> Thanks,
>> Lois
>