Hacktoberfest 2026: los issues que los mantenedores marcaron para octubre, abiertos y aptos para principiantes. Explorar issues de Hacktoberfest

JIT: the EIGS_JIT_HOT 'native-byte share' metric weights chunks by frame entries, ignoring back-edges and OSR — reads 100% on a program that is ~0% native by that measure

Abierto
  • ¿Algo no está bien?
#1,179 0 comentarios 0 reacciones 0 asignados Ver en GitHub

Los mantenedores suelen responder en 1 día

Nadie ha tomado este issue todavía.

Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
52/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
c
Área
compilers, performance

Línea de trabajo

Reproduce the EIGS_JIT_HOT output with tests/bench_dmg_shape.eigs, then trace the aggregate’s use of exec_count, advance, back_edge_count, and OSR coverage. Establish whether the metric can defensibly represent executed native and total bytes, including loop back-edges and OSR thunks, and verify that the resulting report no longer gives the documented misleading share or that the metric is removed.

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

Descripción

area:jit found-by:critic kind:gate-defect

The native-byte share aggregate at the foot of the EIGS_JIT_HOT dump weights every chunk by exec_count — frame entries — when the quantity it claims to report is executed bytecode bytes:

bytes_native += r->exec_count * (uint64_t)r->advance;
bytes_total  += r->exec_count * (uint64_t)r->code_len;

A chunk entered once that then runs a hot loop for 565k back-edges contributes 1 * code_len. On tests/bench_dmg_shape.eigs that is the whole program:

<module>    1  ?   0.0%    0   636   0.0%  565536  yes    61    56  <end>
native-byte share (top 9 hot): 100.0%   (all 9 chunks): 100.0%

The 100% is an artifact — the module's 565k loop iterations count as 636 bytes against 17.6M from the opN callees, so the one chunk that dominates the run is rounded out of the metric.

Two errors compound:

  1. Back-edges are not counted. back_edge_count is tracked per chunk and ignored by the aggregate.
  2. OSR coverage is not counted. The advance term uses jit_advance only. A chunk whose work is entirely inside an OSR thunk (osr=yes, oadv=61 above) scores 0% native while running native.

So the number that should answer "would extending the JIT prefix pay?" understates loop-heavy programs and overstates call-heavy ones. On DMG it reads 46.0% — and perf says 9.9% of samples are actually in JIT'd code, so it is not usable as a proxy for time either.

A defensible version weights each chunk's native/total bytes by an estimate of bytes actually executed (entries for straight-line prefixes, back-edges for loop bodies, and the OSR thunk's advance where an OSR slot is live), or the metric is dropped in favour of the perf attribution it is trying to approximate.

Context: the dump itself only started producing output again in #1176 — this metric has never been read against a real workload.

Lenguaje dominante
C
Estrellas
3
Forks
7
Merge medio
3 h 58 min
PR fusionados (30 d)
105

Preparar el entorno

Abrir en Codespaces

Inicia el contenedor de desarrollo del proyecto en tu navegador, con tu propia cuenta de GitHub.

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 InauguralSystems/EigenScript

Todos los issues de InauguralSystems/EigenScript

Issues similares

Más issues de C

Recibe los nuevos issues en tu correo

Un resumen breve de issues de GitHub para principiantes.