RFR 6642881: Improve performance of Class.getClassLoader()

[roger riggs]

Hi Colleen,

In Class.java, if only the VM creates Class objects  (comment at line 681),
and it does not use the constructor then the code (line 136) in the 
constructor
to set classloader is misleading and deserves a comment.

Roger

On 6/16/2014 1:45 PM, Lois Foltan wrote:
> Hi Coleen,
> This looks good.
> Lois
>
> On 6/16/2014 11:42 AM, Coleen Phillimore wrote:
>> Summary: Add classLoader to java/lang/Class instance for fast access
>>
>> In order to improve performance of Class.getClassLoader() in a way to 
>> allow the compilers to automatically optimize this call, I added the 
>> classLoader to the instance of java/lang/Class.  For microbenchmarks, 
>> this results in a 98% improvement, which was expected.  For Oracle 
>> internal applications, this results in a 10-12% improvement on 
>> solaris/sparc.   The increase in size of java/lang/Class can be 
>> offset by other changes (removing constant pool lock, or removing 
>> signers).
>>
>> See bug link https://bugs.openjdk.java.net/browse/JDK-6642881 and 
>> associated linked bugs for more details.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/6642881_hotspot/
>> open webrev at http://cr.openjdk.java.net/~coleenp/6642881_jdk/
>>
>> There is both hotspot and jdk changes for this change.  The hotspot 
>> changes can work without the jdk changes (check for optional field), 
>> but not vice-versa.  I'll file another bug (and compatibility 
>> request) to remove JVM_GetClassLoader from hotspot.
>>
>> Tested with jck lang, vm, api/java_lang tests with/without jdk 
>> change, nsk vm.quick.testlist and hotspot jtreg tests, and jprt.
>>
>> Thanks,
>> Coleen
>>
>>
>