[14] RFR 8237396: JvmtiTagMap::weak_oops_do() should not trigger barriers

[Zhengyu Gu]

Thanks, Stefan.

-Zhengyu

On 1/20/20 8:03 AM, Stefan Karlsson wrote:
> Hi Zhengyu,
> 
> On 2020-01-17 16:28, Zhengyu Gu wrote:
>> Please review this small patch that avoids barriers in 
>> JvmtiTagMap::weak_oops_do() method.
>>
>> The method is used by GC and GC expects to see raw oops.
> 
> For the record, ZGC doesn't require to see raw oops here. The 
> unnecessary load barriers will simply pre-clean the oops before the 
> closures are applied.
> 
>>
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8237396
>> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8237396/webrev.00/
> 
> Looks good.
> 
> I've tested with ZGC as well.
> 
> Thanks,
> StefanK
> 
>>
>> Test:
>>    hotspot_gc
>>    vmTestbase_nsk_jvmti
>>    (fastdebug and release) on x86_64 Linux
>>
>>    Submit test in progress.
>>
>> Thanks,
>>
>> -Zhengyu
>>
>