Host zerocopy path: bundle deregistration acks instead of one NcpyOperationInfo message per buffer

Abierto
  • ¿Algo no está bien?
#3,964 0 comentarios 0 reacciones 0 asignados Ver en GitHub

Los mantenedores suelen responder en 1 día

Nadie ha tomado este issue todavía.

Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
22/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Tranquilo
Stack tecnológico
cpp, hpc
Área
distributed-systems, hpc, networking

Línea de trabajo

Start from handleEntryMethodApiCompletion on the host RDMA path, where one CmiInvokeRemoteDeregAckHandler / NcpyOperationInfo reverse message is sent per completed buffer, then compare with the id-and-piggyback scheme already used on the device path in #3961. Keep remoteDeregHandler's two guards (compare by node not PE; never re-enter the completion path). Carry the 8-byte id block on the nocopy metadata message rather than the converse header. Done when host-path deregistration and source callbacks match the device path's bundled acks without extra per-buffer messages on the critical path.

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

Descripción

Host zerocopy path: bundle deregistration acks instead of one NcpyOperationInfo message per buffer

On the host RDMA path, handleEntryMethodApiCompletion sends one reverse message per completed buffer (CmiInvokeRemoteDeregAckHandler, carrying the whole NcpyOperationInfo, about 200 bytes) so the source PE can deregister and then invoke the source callback (remoteDeregHandler). That is one message per buffer per message, on the critical path of the source PE.

The device path now does the same job with an 8-byte id per buffer, minted on the sender and resolved there, carried back inside the first descriptor of the next zerocopy message the receiver sends to that PE (capacity 8, count-prefixed), with a standalone message only on overflow or at idle (#3961). Measured on Frontier (8x MI250X, Slingshot, Jacobi with 2-16 KB ghosts): the release went from ~4 us per remote message to ~0.3 us, and a requested source callback from 6-20% of a chare-iteration to 3-4%.

Nothing in that mechanism is device-specific: the id table, the per-destination accumulator, and the block on the descriptor would carry a host buffer's release and callback just as well. Proposal: give the host path the same id-and-piggyback scheme, keeping remoteDeregHandler's two guards (compare by node, not PE; never re-enter the completion path, which loops and leaks a QdCreate per pass), and carry the block on the nocopy metadata message rather than in the converse header.

Not done in #3961 on purpose: it touches the host path's completion state machine and deserves its own review.

Lenguaje dominante
C++
Estrellas
241
Forks
62
Merge medio
1 d 1 h
PR fusionados (30 d)
125

Preparar el entorno

Este proyecto no incluye contenedor de desarrollo, Dockerfile ni guía de contribución, así que la configuración corre por tu cuenta: empieza por su README y consulta nuestra guía para la primera contribución para los pasos generales.

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

Más de charmplusplus/charm

Todos los issues de charmplusplus/charm

Issues similares

Más issues de C++

Recibe los nuevos issues en tu correo

Un resumen breve de issues de GitHub para principiantes.