FFM performance tweaks

[Maurizio Cimadamore]

Thanks Brian

On 19/11/2024 15:35, Brian S O'Neill wrote:
> I've already been running some tests against build 24 to see what 
> affect pull 21810 has. Tests using the transformed VarHandle technique 
> didn't show much improvement. 
I believe that's to be expected.
> I just started running tests which access the (effectively) unbounded 
> MemorySegment and will report back in about an hour.

That would be the more interesting one, yes. That said, I'm kind of 
prepared not to see the gains in the synthetic benchmark to translate in 
bigger real world gains (but I'd be very happy to be wrong here :) ).

Maurizio

>
> On 2024-11-19 06:42 AM, Maurizio Cimadamore wrote:
>> Hi,
>> some performance tweaks have landed in the JDK 24 early access build 
>> (build 24):
>>
>> https://jdk.java.net/24/
>>
>> They are:
>>
>> https://git.openjdk.org/jdk/pull/21764
>> https://git.openjdk.org/jdk/pull/21810
>>
>> The former contains some optimizations for `MemorySegment
>>
>> ` which should improve scalarization - see [1]. The second contains 
>> an improvement to the way we perform the liveness check, which should 
>> make such check provably redundant for segments backed by the global 
>> arena. This should improve the performance of workarounds using an 
>> “everything” segment to access off-heap memory with minimal impact 
>> from bound checks [2].
>>
>> As JDK 24 is moving closer to rampdown phase [3], it would be great 
>> to give such changes a try and report back.
>>
>> Cheers
>> Maurizio
>>
>> [1] - 
>> https://mail.openjdk.org/pipermail/panama-dev/2024-October/020702.html
>> [2] - 
>> https://mail.openjdk.org/pipermail/panama-dev/2024-October/020736.html
>> [3] - https://openjdk.org/projects/jdk/24/
>>
>> ​
>>
>> ​
>
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