[lworld] Integrated: 8369923: [lworld] Hot call to Unsafe.isFlatField in serialization

[Chen Liang]

On Mon, 13 Oct 2025 19:53:27 GMT, Chen Liang <liach at openjdk.org> wrote:

> There's a spike of calls to `Unsafe.isFlatField` in serialzation workloads. The layout information can be prepared with FieldReflector and cached. CI looks good, need to verify the regression is fixed.
> 
> The old perfasm profile was:
> ....[Hottest Regions]...............................................................................
>    4.66% libjvm.so Unsafe_IsFlatField
>    4.13% c2, level 4 java.io.ObjectOutputStream::writeObject0, version 6, compile id 2698
>    3.72% c2, level 4 java.io.ObjectInputStream$BlockDataInputStream::readUTFSpan, version 2, compile id 1878
>    3.61% c2, level 4 java.io.ObjectInputStream$PeekInputStream::readFully, version 2, compile id 1902

This pull request has now been integrated.

Changeset: d7e2c65a
Author:    Chen Liang <liach at openjdk.org>
URL:       https://git.openjdk.org/valhalla/commit/d7e2c65a733d8e40e06a9bb3ea474b525a672290
Stats:     9 lines in 1 file changed: 4 ins; 0 del; 5 mod

8369923: [lworld] Hot call to Unsafe.isFlatField in serialization

Reviewed-by: rriggs

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PR: https://git.openjdk.org/valhalla/pull/1676