RFR: 8252103: Parallel heap inspection for ParallelScavengeHeap [v12]

[Lin Zang]

On Tue, 3 Nov 2020 20:02:00 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Lin Zang has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remove unnecessary newline symbol in assertion
>
> src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp line 581:
> 
>> 579:       old_gen()->block_iterate(cl, (size_t)block_index);
>> 580:     }
>> 581:   }
> 
> The structure seems to suggest that each `if` case could be hit in every iteration, but actually only the third case will be revisited more than once. I wonder if this could be made more explicit.

Thanks Albert! Correct, the OldGen part will be revisit much for frequently.  do you have any clue to optimize this? I was considering the marco like "likely()" but I am not sure whether it is acceptable for hotspot.

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PR: https://git.openjdk.java.net/jdk/pull/25