ci: shard bpf-tests by integration test binary

.github/actions/install-rust/action.yml

@@ -5,6 +5,10 @@ inputs:
     description: Comma-separated list of additional rustup components to install (e.g. "rustfmt, clippy").
     required: false
     default: ""
+  cache-key:
+    description: Extra value appended to the rust-cache key, used to give matrix shards distinct caches and avoid concurrent save races.
+    required: false
+    default: ""
 runs:
   using: composite
   steps:
@@ -16,3 +20,5 @@ runs:
       shell: bash
       run: echo "${{ inputs.components }}" | tr ',' '\n' | xargs rustup component add
     - uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4 # v2
+      with:
+        key: ${{ inputs.cache-key }}

.github/workflows/ci.yml

@@ -87,12 +87,21 @@ jobs:
 
   bpf-tests:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Each memtrack integration test binary runs its cases serially
+        # (eBPF tracker can't overlap with itself in one process), so we
+        # shard at the test-binary level to parallelize across jobs.
+        test: [c_tests, cpp_tests, rust_tests, spawn_tests]
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           lfs: true
           submodules: true
       - uses: ./.github/actions/install-rust
+        with:
+          cache-key: ${{ matrix.test }}
       - name: Install dependencies required for libbpf-sys (vendored feature)
         run: sudo apt-get update && sudo apt-get install -y autopoint bison flex
 
@@ -102,7 +111,7 @@ jobs:
       - name: Run tests
         env:
           RUST_LOG: debug
-        run: sudo -E $(which cargo) test -- --test-threads 1 --nocapture
+        run: sudo -E $(which cargo) test --lib --test ${{ matrix.test }} -- --test-threads 1 --nocapture
         working-directory: crates/memtrack
 
       # Since we ran the tests with sudo, the build artifacts will have root ownership