RFR: JDK-8199406: Performance drop with Java JDK 1.8.0_162-b32

[Poonam Parhar]

Hello Vladimir,

Thanks for reviewing the changes. Please find the updated webrev here:
http://cr.openjdk.java.net/~poonam/8199406/webrev.01/

Regards,
Poonam

On 3/29/2018 2:23 PM, Vladimir Kozlov wrote:
> Looks good. I have few comments.
>
> You can remove old is_entry_point() which have the same code as new 
> entry_point(). After changes it is used only in one place in 
> CompiledIC::is_megamorphic(). It can be replace with NULL check of 
> entry_point() result there. Add comment in vtableStubs.hpp for new 
> method.
>
> is_metadata_method field name should start with _ (this is Hotspot 
> convention).
>
> is_loader_alive() could be simplified since you have field now:
>
>   inline bool is_loader_alive(BoolObjectClosure* is_alive) {
>     Klass* k = is_metadata_method ? 
> ((Method*)_holder_metadata)->method_holder() : (Klass*)_holder_metadata;
>     if (!k->is_loader_alive(is_alive)) {
>       return false;
>     }
>     if (!_holder_klass->is_loader_alive(is_alive)) {
>       return false;
>     }
>     return true;
>   }
>
> Thanks,
> Vladimir
>
> On 3/29/18 1:31 PM, Poonam Parhar wrote:
>> Hello,
>>
>> Please review the changes for the following bug that improve the 
>> nmethod unloading times with a couple of optimizations.
>>
>> JDK-8199406 <https://bugs.openjdk.java.net/browse/JDK-8199406>: 
>> Performance drop with Java JDK 1.8.0_162-b32
>> Webrev: http://cr.openjdk.java.net/~poonam/8199406/webrev.00/
>>
>> This changeset includes two changes:
>> 1. In /compiledIC.cpp, CompiledIC::is_icholder_entry()/ , we need to 
>> determine if the code blob is an itable stub. With this change, 
>> before linearly searching through all the VtableStub entries, we 
>> first check whether the codeblob is a vtable or not. We now also 
>> parse through the list entries only once rather than doing it twice 
>> in /VtableStubs::is_entry_point()/ and /VtableStubs::stub_containing()/.
>> 2. The second change helps avoid the virtual function calls in 
>> CompiledICHolder::is_loader_alive(). CompiledICHolder now stores 
>> information whether the metadata it holds is a method or a klass.
>>
>> Testing:
>> - Customer testing confirming that their class-unloading times drop 
>> from 10s of seconds to an average of 0.75 secs.
>> - mach5 jdk-tier1,jdk-tier2,jdk-tier3,hs-tier1,hs-tier2
>>
>> Thanks,
>> Poonam
>>