RFR: 8293416: ZGC: Set mark bit with unconditional atomic ops [v3]

[hev]

On Fri, 9 Sep 2022 10:26:45 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> hev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:
>> 
>>  - ZGC: Set mark bit with unconditional atomic ops
>>  - BitMap: Set bit with unconditional atomic ops
>>  - Atomic: Add bitset functions
>
> src/hotspot/share/gc/z/zBitMap.inline.hpp line 67:
> 
>> 65:     inc_live = false;
>> 66:     return false;
>> 67:   }
> 
> The fast/slow paths are almost identical. I believe some numbers would be nice to justify the presence of the fast path.

I think so. Atomic operations are more expensive than normal memory loads. This is why should split to fast and slow path, although they are almost Identical. The micro benchmark 2 shows it.

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PR: https://git.openjdk.org/jdk/pull/10182