fix(core): exclude the running node executable from callgrind

The runner only passes `--obj-skip` for the `node` it resolves on PATH.
When benchmarks run another binary, such as one provided by a Bazel
toolchain, callgrind records the whole V8 runtime between the JS frames:
thousands of native functions that drown the flamegraph and make it
expensive to process.

Register `process.execPath` on callgrind's obj-skip list in `setupCore`,
through the instrument-hooks client request, as pytest-codspeed does for
the Python executable. It runs before any benchmark starts the
instrumentation, and is a no-op outside Valgrind.

Author: not-matthias

packages/core/src/index.ts

@@ -26,6 +26,8 @@ export const setupCore = () => {
   }
 
   native_core.InstrumentHooks.setIntegration("codspeed-node", __VERSION__);
+  // The `node` on the runner's PATH may not be the one executing (e.g. Bazel), so skip the real one.
+  native_core.InstrumentHooks.callgrindAddObjSkip(process.execPath);
   // In walltime, we use node's native profiling options rather than our own, cf `getV8Flags`
   if (getCodspeedRunnerMode() !== "walltime") {
     linuxPerf.start();

packages/core/src/native_core/index.ts

@@ -67,6 +67,10 @@ try {
       addMarker: (_pid: number, _markerType: number, _timestamp: bigint) => {
         return 0;
       },
+      // eslint-disable-next-line @typescript-eslint/no-unused-vars
+      callgrindAddObjSkip: (_path: string) => {
+        return 0;
+      },
       __codspeed_root_frame__: <T>(callback: () => T): T => {
         return callback();
       },

packages/core/src/native_core/instruments/hooks.ts

@@ -63,6 +63,15 @@ export interface InstrumentHooks {
    */
   addMarker(pid: number, markerType: number, timestamp: bigint): number;
 
+  /**
+   * Add an object file to callgrind's obj-skip list, as `--obj-skip` does.
+   * Only affects code callgrind has not instrumented yet. No-op outside
+   * Valgrind.
+   * @param path Path of the object file, resolved to its real path
+   * @returns 0 on success, non-zero on error
+   */
+  callgrindAddObjSkip(path: string): number;
+
   /**
    * Execute a callback function with __codspeed_root_frame__ in its stack trace
    * @param callback Function to execute

packages/core/src/native_core/instruments/hooks_wrapper.cc

@@ -135,6 +135,27 @@ Napi::BigInt CurrentTimestamp(const Napi::CallbackInfo &info) {
   return Napi::BigInt::New(env, ts);
 }
 
+Napi::Number CallgrindAddObjSkip(const Napi::CallbackInfo &info) {
+  Napi::Env env = info.Env();
+
+  if (info.Length() != 1) {
+    Napi::TypeError::New(env, "Expected 1 argument: path")
+        .ThrowAsJavaScriptException();
+    return Napi::Number::New(env, 1);
+  }
+
+  if (!info[0].IsString()) {
+    Napi::TypeError::New(env, "Expected string (path)")
+        .ThrowAsJavaScriptException();
+    return Napi::Number::New(env, 1);
+  }
+
+  std::string path = info[0].As<Napi::String>().Utf8Value();
+
+  uint8_t result = instrument_hooks_callgrind_add_obj_skip(path.c_str());
+  return Napi::Number::New(env, result);
+}
+
 Napi::Number AddMarker(const Napi::CallbackInfo &info) {
   Napi::Env env = info.Env();
 
@@ -220,6 +241,8 @@ Napi::Object Initialize(Napi::Env env, Napi::Object exports) {
                          Napi::Function::New(env, CurrentTimestamp));
   instrumentHooksObj.Set(Napi::String::New(env, "addMarker"),
                          Napi::Function::New(env, AddMarker));
+  instrumentHooksObj.Set(Napi::String::New(env, "callgrindAddObjSkip"),
+                         Napi::Function::New(env, CallgrindAddObjSkip));
   instrumentHooksObj.Set(Napi::String::New(env, "__codspeed_root_frame__"),
                          Napi::Function::New(env, __codspeed_root_frame__));
 

packages/core/src/native_core/instruments/hooks_wrapper.h

@@ -21,6 +21,7 @@ Napi::Number SetEnvironment(const Napi::CallbackInfo &info);
 Napi::Number WriteEnvironment(const Napi::CallbackInfo &info);
 Napi::BigInt CurrentTimestamp(const Napi::CallbackInfo &info);
 Napi::Number AddMarker(const Napi::CallbackInfo &info);
+Napi::Number CallgrindAddObjSkip(const Napi::CallbackInfo &info);
 Napi::Object Initialize(Napi::Env env, Napi::Object exports);
 
 } // namespace hooks_wrapper