fix(ci): partition GHA sccache cache per arch in shadow spike#961
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fix(ci): partition GHA sccache cache per arch in shadow spike#961
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Without a per-arch SCCACHE_GHA_VERSION, both matrix jobs (linux-amd64-cpu8 and linux-arm64-cpu8) target the same GHA cache key. Run 1 on 2026-04-24 showed this concretely: arm64 started first and landed 575/1064 cache writes; amd64 started ~1 min later and every one of its 1062 writes failed, leaving the cache with no amd64 entries at all. Partitioning by matrix.runner ensures each arch gets its own cache namespace, letting us see real warm-cache behavior on the subsequent Run 2-4 dispatches. Signed-off-by: Jonas Toelke <jtoelke@nvidia.com>
pimlock
approved these changes
Apr 24, 2026
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Summary
Run 1 of
shadow-shared-cpu-spikeon 2026-04-24 (run 24890968200) succeeded on wall time but exposed a cache-key collision: both matrix jobs wrote to the same GHA cache key because we didn't partition by arch. arm64 started first and landed 575/1064 writes; amd64 started ~60s later and every one of its 1062 writes failed (409 Conflict on keys already claimed by arm64).Fix: add job-level
SCCACHE_GHA_VERSION: \${{ matrix.runner }}so each arch gets its own cache namespace. One-liner (plus comment).Related Issue
OS-49 runner migration, Phase 2 / OS-126. Unblocks the real warm-cache behavior on Run 2-4 dispatches.
Changes
.github/workflows/shadow-shared-cpu-spike.yml: new job-level `env.SCCACHE_GHA_VERSION` keyed to `${{ matrix.runner }}`. Workflow-level `env` can't reference `matrix.*`, hence the job-level placement.Testing
Context — Run 1 data (cache-side is void, wall/queue are good)
Wall time comfortably below the exit-criterion threshold even on cold cache — the real question left is whether warm cache holds up, which this PR unblocks.
Checklist