workflows/eval: disable swap (#431459)

.github/workflows/eval.yml

@@ -32,12 +32,11 @@ jobs:
     outputs:
       targetRunId: ${{ steps.targetRunId.outputs.targetRunId }}
     steps:
-      - name: Enable swap
+      # We'd rather fail than run slow eval on swap.
+      # Failing allows us to adjust the chunkSize to remain fast.
+      - name: Disable swap
         run: |
-          sudo fallocate -l 10G /swap
-          sudo chmod 600 /swap
-          sudo mkswap /swap
-          sudo swapon /swap
+          sudo swapoff -a
 
       - name: Check out the PR at the test merge commit
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -56,7 +55,7 @@ jobs:
         run: |
           nix-build untrusted/ci -A eval.singleSystem \
             --argstr evalSystem "$MATRIX_SYSTEM" \
-            --arg chunkSize 10000 \
+            --arg chunkSize 8000 \
             --out-link merged
           # If it uses too much memory, slightly decrease chunkSize