ADR-0023 D9: blocking credit-emit with full-path latency

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PE_IPCQ._handle_recv now yields-from _delayed_credit_send instead of
spawning it as a fork, so the receiver's pe_exec_ns includes the
credit-return cost. _credit_latency_ns switches from
compute_drain_ns(path, 16) to compute_path_latency_ns(path, 16) and
fixes a latent find_path bug where the destination lacked the
".pe_dma" suffix (silently returned 0 ns under the bare except).

Net effect on h3/h4 inter-cube pe-to-pe latency: IPCQ >= raw DMA at
every size, matching real-HW posted-write semantics. tl.send remains
fire-and-forget. ADR-0023 D9 amended; new diagnostic test
tests/test_pe_to_pe_diagnostic.py captures per-PE pe_exec_ns, paths,
drain, and meta-arrival timing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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This commit is contained in:

Mukesh Garg

2026-04-27 15:12:38 -07:00

parent 19dfc86dc3

commit 90874abbfe

11 changed files with 901 additions and 25 deletions

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tests/pe2pe_latency_plots/h3_inter_cube_horizontal.png

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