aduh95 · aduh95 · May 28, 2026 · Aug 28, 2025 · May 28, 2026
diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
@@ -0,0 +1,206 @@
+name: Benchmark
+
+on:
+  workflow_dispatch:
+    inputs:
+      repo:
+        type: string
+        description: GitHub repository to fetch from (default to the current repo)
+      pr_id:
+        type: number
+        required: true
+        description: The PR to test
+      commit:
+        required: true
+        type: string
+        description: The expect HEAD of the PR
+      category:
+        required: true
+        type: string
+        description: The category (or categories) of tests to run, for example buffers, cluster etc. Maps to a folders in node/benchmark
+      filter:
+        type: string
+        description: A substring to restrict the benchmarks to run in a category. e.g. `net-c2c`
+      runs:
+        type: number
+        default: 30
+        description: How many times to repeat each benchmark
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    strategy:
+      fail-fast: true
+      matrix:
+        include:
+          - runner: ubuntu-24.04
+            system: x86_64-linux
+          - runner: ubuntu-24.04-arm
+            system: aarch64-linux
+          - runner: macos-15-intel
+            system: x86_64-darwin
+          - runner: macos-latest
+            system: aarch64-darwin
+    name: '${{ matrix.system }}: with shared libraries'
+    runs-on: ${{ matrix.runner }}
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
+        with:
+          repository: ${{ inputs.repo || github.repository }}
+          ref: refs/pull/${{ inputs.pr_id }}/merge
+          persist-credentials: false
+          fetch-depth: 2
+
+      - name: Validate PR head and roll back to base commit
+        run: |
+          [ "$(git rev-parse HEAD^2)" = "$EXPECTED_SHA" ]
+          git reset HEAD^ --hard
+        env:
+          EXPECTED_SHA: ${{ inputs.commit }}
+
+      - uses: cachix/install-nix-action@96951a368ba55167b55f1c916f7d416bac6505fe  # v31.10.3
+        with:
+          extra_nix_config: sandbox = true
+
+      - uses: cachix/cachix-action@1eb2ef646ac0255473d23a5907ad7b04ce94065c  # v17
+        with:
+          # We do not pass any `authToken` to avoid polluting the cache with potentially untrusted code.
+          name: nodejs
+
+      - name: Configure sccache
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd  # v8.0.0
+        with:
+          script: |
+            core.exportVariable('SCCACHE_GHA_VERSION', 'on');
+            core.exportVariable('ACTIONS_CACHE_SERVICE_V2', 'on');
+            core.exportVariable('ACTIONS_RESULTS_URL', process.env.ACTIONS_RESULTS_URL || '');
+            core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env.ACTIONS_RUNTIME_TOKEN || '');
+
+      - name: Build Node.js on the base commit
+        run: |
+          nix-shell \
+            -I nixpkgs=./tools/nix/pkgs.nix \
+            --pure --keep TAR_DIR --keep FLAKY_TESTS \
+            --keep SCCACHE_GHA_ENABLED --keep ACTIONS_CACHE_SERVICE_V2 --keep ACTIONS_RESULTS_URL --keep ACTIONS_RUNTIME_TOKEN \
+            --arg useSeparateDerivationForV8 true \
+            --arg loadJSBuiltinsDynamically false \
+            --arg ccache "${NIX_SCCACHE:-null}" \
+            --arg devTools '[]' \
+            --arg benchmarkTools '[]' \
+            --run '
+                make build-ci -j4 V=1
+            '
+          mv out/Release/node base_node
+
+      - name: Checkout the merge commit
+        run: git reset FETCH_HEAD --hard
+
+      - name: Re-build Node.js on the merge commit
+        # ccache is disabled here to avoid polluting the cache. Local build outputs should make this build relatively quick anyway.
+        if: ${{ github.event_name == 'workflow_dispatch' }}
+        run: |
+          nix-shell \
+            -I nixpkgs=./tools/nix/pkgs.nix \
+            --pure \
+            --arg useSeparateDerivationForV8 true \
+            --arg loadJSBuiltinsDynamically false \
+            --arg ccache 'null' \
+            --arg devTools '[]' \
+            --arg benchmarkTools '[]' \
+            --run '
+                make -j4 V=1
+            '
+
+      - name: Run benchmark
+        if: ${{ github.event_name == 'workflow_dispatch' }}
+        run: |
+          nix-shell \
+            -I nixpkgs=./tools/nix/pkgs.nix \
+            --pure --keep FILTER --keep LC_ALL --keep LANG \
+            --arg loadJSBuiltinsDynamically false \
+            --arg ccache 'null' \
+            --arg icu 'null' \
+            --arg sharedLibDeps '{}' \
+            --arg devTools '[]' \
+            --run '
+                set -o pipefail
+                ./base_node benchmark/compare.js \
+                  --filter "$FILTER" \
+                  --runs ${{ inputs.runs }} \
+                  --old ./base_node --new ./node \
+                  -- ${{ inputs.category }} \
+                | tee /dev/stderr \
+                > ${{ matrix.system }}.csv
+                echo "> [!WARNING] "
+                echo "> Do not take GHA benchmark results as face value, always confirm them"
+                echo "> using a dedicated machine, e.g. Jenkins CI."
+                echo
+                echo "Benchmark results:"
+                echo
+                echo '"'"'```'"'"'
+                Rscript benchmark/compare.R < ${{ matrix.system }}.csv
+                echo '"'"'```'"'"'
+                echo
+                echo "> [!WARNING] "
+                echo "> Do not take GHA benchmark results as face value, always confirm them"
+                echo "> using a dedicated machine, e.g. Jenkins CI."
+            ' | tee /dev/stderr >> "$GITHUB_STEP_SUMMARY"
+        env:
+          FILTER: ${{ inputs.filter }}
+
+      - name: Upload raw benchmark results
+        if: ${{ github.event_name == 'workflow_dispatch' }}
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
+        with:
+          name: csv-${{ matrix.system }}
+          path: ${{ matrix.system }}.csv
+
+  aggregate-benchmark-results:
+    needs: build
+    name: Aggregate benchmark results
+    if: ${{ github.event_name == 'workflow_dispatch' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
+        with:
+          persist-credentials: false
+          sparse-checkout: |
+            benchmark/*.R
+            tools/nix/*.nix
+            *.nix
+          sparse-checkout-cone-mode: false
+
+      - name: Download benchmark raw results
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
+        with:
+          pattern: csv-*
+          merge-multiple: true
+          path: raw-results
+
+      - uses: cachix/install-nix-action@96951a368ba55167b55f1c916f7d416bac6505fe  # v31.10.3
+        with:
+          extra_nix_config: sandbox = true
+
+      - name: Benchmark results
+        run: |
+          nix-shell \
+            -I nixpkgs=./tools/nix/pkgs.nix \
+            --pure --keep LC_ALL --keep LANG \
+            -E '(import <nixpkgs> {}).mkShell { buildInputs = import ./tools/nix/benchmarkTools.nix { withHttpBenchmarkDeps = false; }; }' \
+            --run '
+                echo "> [!WARNING] "
+                echo "> Do not take GHA benchmark results as face value, always confirm them"
+                echo "> using a dedicated machine, e.g. Jenkins CI."
+                echo
+                echo "Benchmark results:"
+                echo
+                echo '"'"'```'"'"'
+                awk "FNR==1 && NR!=1{next;}{print}" raw-results/*.csv | Rscript benchmark/compare.R
+                echo '"'"'```'"'"'
+                echo
+                echo "> [!WARNING] "
+                echo "> Do not take GHA benchmark results as face value, always confirm them"
+                echo "> using a dedicated machine, e.g. Jenkins CI."
+            ' | tee /dev/stderr >> "$GITHUB_STEP_SUMMARY"
diff --git a/lib/internal/util.js b/lib/internal/util.js
@@ -536,21 +536,6 @@ function promisify(original) {
 
 promisify.custom = kCustomPromisifiedSymbol;
 
-// The built-in Array#join is slower in v8 6.0
-function join(output, separator) {
-  let str = '';
-  if (output.length !== 0) {
-    const lastIndex = output.length - 1;
-    for (let i = 0; i < lastIndex; i++) {
-      // It is faster not to use a template string here
-      str += output[i];
-      str += separator;
-    }
-    str += output[lastIndex];
-  }
-  return str;
-}
-
 // As of V8 6.6, depending on the size of the array, this is anywhere
 // between 1.5-10x faster than the two-arg version of Array#splice()
 function spliceOne(list, index) {
@@ -1005,7 +990,6 @@ module.exports = {
   isUnderNodeModules,
   isMacOS,
   isWindows,
-  join,
   lazyDOMException,
   lazyDOMExceptionClass,
   normalizeEncoding,

diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
@@ -151,7 +151,6 @@ const {
 const {
   customInspectSymbol,
   isError,
-  join,
   removeColors,
 } = require('internal/util');
 
@@ -2668,7 +2667,7 @@ function reduceToSingleString(
         const start = output.length + ctx.indentationLvl +
                       braces[0].length + base.length + 10;
         if (isBelowBreakLength(ctx, output, start, base)) {
-          const joinedOutput = join(output, ', ');
+          const joinedOutput = ArrayPrototypeJoin(output, ', ');
           if (!StringPrototypeIncludes(joinedOutput, '\n')) {
             return `${base ? `${base} ` : ''}${braces[0]} ${joinedOutput}` +
               ` ${braces[1]}`;
@@ -2679,12 +2678,12 @@ function reduceToSingleString(
     // Line up each entry on an individual line.
     const indentation = `\n${StringPrototypeRepeat(' ', ctx.indentationLvl)}`;
     return `${base ? `${base} ` : ''}${braces[0]}${indentation}  ` +
-      `${join(output, `,${indentation}  `)}${indentation}${braces[1]}`;
+      `${ArrayPrototypeJoin(output, `,${indentation}  `)}${indentation}${braces[1]}`;
   }
   // Line up all entries on a single line in case the entries do not exceed
   // `breakLength`.
   if (isBelowBreakLength(ctx, output, 0, base)) {
-    return `${braces[0]}${base ? ` ${base}` : ''} ${join(output, ', ')} ` +
+    return `${braces[0]}${base ? ` ${base}` : ''} ${ArrayPrototypeJoin(output, ', ')} ` +
       braces[1];
   }
   const indentation = StringPrototypeRepeat(' ', ctx.indentationLvl);
@@ -2694,7 +2693,7 @@ function reduceToSingleString(
   const ln = base === '' && braces[0].length === 1 ?
     ' ' : `${base ? ` ${base}` : ''}\n${indentation}  `;
   // Line up each entry on an individual line.
-  return `${braces[0]}${ln}${join(output, `,\n${indentation}  `)} ${braces[1]}`;
+  return `${braces[0]}${ln}${ArrayPrototypeJoin(output, `,\n${indentation}  `)} ${braces[1]}`;
 }
 
 function hasBuiltInToString(value) {

diff --git a/tools/nix/benchmarkTools.nix b/tools/nix/benchmarkTools.nix
@@ -1,9 +1,11 @@
 {
   pkgs ? import ./pkgs.nix { },
+  withHttpBenchmarkDeps ? true,
 }:
 [
   pkgs.R
   pkgs.rPackages.ggplot2
   pkgs.rPackages.plyr
-  pkgs.wrk
 ]
+++ pkgs.lib.optional withHttpBenchmarkDeps pkgs.wrk
+++ pkgs.lib.optional pkgs.stdenv.buildPlatform.isLinux pkgs.glibcLocales
diff --git a/tools/nix/v8.nix b/tools/nix/v8.nix
@@ -57,10 +57,24 @@ let
         ../../tools/icu/icutrim.py
         ../../tools/icu/no-op.cc
       ];
+      potentiallyAlreadyRemovedFiles =
+        # Files that are removed in the release tarball (see Makefile $(TARBALL) target)
+        [ (fileset.difference ../../deps/v8/test ../../deps/v8/test/torque) ]
+        ++ (builtins.filter builtins.pathExists [
+          ../../deps/v8/samples
+          ../../deps/v8/tools/profviz
+          ../../deps/v8/tools/run-tests.py
+          ../../deps/v8/third_party/ittapi
+        ]);
+      trackedFiles =
+        ({
+          # This line is being modified by Makefile $(TARBALL) target, any change to it should be sync
+          fileset = fileset.intersection (fileset.gitTracked root) (fileset.unions files);
+        }).fileset;
     in
     fileset.toSource {
       inherit root;
-      fileset = fileset.intersection (fileset.gitTracked root) (fileset.unions files);
+      fileset = fileset.difference trackedFiles (fileset.unions potentiallyAlreadyRemovedFiles);
     };
   v8Dir = "${src}/deps/v8";
 in