chore(ci): fix target cpu

.github/workflows/load-nightly.yml

@@ -57,7 +57,15 @@ jobs:
 
       - uses: Swatinem/rust-cache@v2
         with:
-          shared-key: load
+          # Distinct from load-smoke's `load-v2`. Nightly runs on the
+          # self-hosted `nuc-loadtest` runner (homogeneous), where
+          # `-C target-cpu=native` from `.cargo/config.toml` gives the
+          # accurate perf baseline we want. Smoke runs on the GHA
+          # heterogeneous pool with `RUSTFLAGS=-C target-cpu=x86-64-v3`.
+          # Sharing the same cache key would let native-baked proc-macro
+          # dylibs from nightly leak into smoke's restore set → SIGILL
+          # on a leaner GHA runner. Separate namespaces prevent that.
+          shared-key: load-nightly-v2
 
       - name: Install Node 20
         # The self-hosted runner image ships Node 12, which can't parse the

.github/workflows/load-smoke.yml

@@ -18,6 +18,14 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
+  # `.cargo/config.toml` sets `-C target-cpu=native` for dev speed, but
+  # GitHub-hosted runners are a heterogeneous pool — cached rlibs / proc-
+  # macro dylibs baked with AVX-512 on one runner crash with SIGILL when
+  # rustc dlopens them on a leaner one. Env RUSTFLAGS fully replaces the
+  # config.toml value (they don't merge), so pinning to `x86-64-v3` here
+  # (AVX2 baseline — every GHA runner has it) makes cached artifacts
+  # portable across the pool without touching local dev.
+  RUSTFLAGS: "-C target-cpu=x86-64-v3"
 
 jobs:
   smoke:
@@ -31,7 +39,9 @@ jobs:
 
       - uses: Swatinem/rust-cache@v2
         with:
-          shared-key: load
+          # Bumped suffix busts any existing cache poisoned with native-CPU
+          # ISA from a prior build (see RUSTFLAGS note above).
+          shared-key: load-v2
 
       - name: Install k6
         uses: grafana/setup-k6-action@v1