[java][Vector][Performance] PromotableWriter.setPosition resolving to itable dispatch on C2 compiled path.

Abierto

#1,238 abierto el 20/7/2026 0 comentarios 0 reacciones 0 asignados Ver en GitHub

Nadie ha tomado este issue todavía.

Evaluación

Dificultad: 4/5
Tiempo estimado: 3-5 días
Aptitud para principiantes: 45/100

Tipo de issue: Nueva funcionalidad
Claridad: Bastante claro
Estado de actividad: Tranquilo
Stack tecnológico: java
Área: performance

Línea de trabajo

Empieza con PromotableWriter.setPosition(int) y la ruta de llamadas de AbstractFieldWriter descrita en el issue. Reproduce el comportamiento de dispatch usando el benchmark de JMH en el módulo performance y, a continuación, verifica que el cambio resultante mejora el dispatch medido sin regresiones.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Type: enhancement

Describe the enhancement requested

This is my first issue report here. Thanks for all the wonderful work.

Usecase: I am planning to replace our parquet-mr based parquet writer with arrow-java to arrow-rs via SharedMemory IPC. Each Kubernetes pod writes about 3 to 4 thousand event per second per pod. The original schema does have some heavy nesting (thrift influence) and schema redesign while desirable but is a much longer exercise. In the process of proof of concept, was able to get the whole flow working but when running some sample shadow flows, saw that all dispatch via

PromotableWriter.setPosition(int index)

would result in a itable dispatch. Looking at it, there could be multiple implementations of FieldWriter's at callsite and C2 fails to convert it into monomorphic or bimorphic calls. Was able to get a synthetic benchmark setup inside the performance module and can see the same in JMH runs too.

This wonderful writeup by Aleksey Shipilev speaks about it in great detail.
We can convert the itable dispatch to a vtable dispatch by the method to be dispatched over AbstractFieldWriter. I will do more tests around the same and can submit the PR here. Tried searching over the issues and this doesn't seem to have been reported so far. Just curious if I am doing something wrong when using ListVector's (and hence holding back attaching the PR straight away!).

Just pasting the screen grab of the actual struct writer used in the benchmark. The benchmark is produced by claude (as one can make it out looking at the comments, but it seemed pretty ok to me).