perf_hooks: only enable GC tracking when it's requested

Previously a GC prologue callback and a GC epilogue callback are always unconditionally enabled during bootstrap when the `performance` binding is loaded, even when the user does not use the performance timeline API to enable GC tracking. This patch makes the callback addition conditional and only enables them when the user explicitly requests `observer.observe(['gc'])` to avoid the overhead. PR-URL: #25853 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Gus Caplan <[email protected]> Reviewed-By: James M Snell <[email protected]>
nodejs · Feb 6, 2019 · e81c6c8 · e81c6c8
1 parent b7fb49e
commit e81c6c8
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Showing 2 changed files with 14 additions and 4 deletions.
diff --git a/lib/perf_hooks.js b/lib/perf_hooks.js
@@ -11,7 +11,8 @@ const {
   timeOrigin,
   timeOriginTimestamp,
   timerify,
-  constants
+  constants,
+  setupGarbageCollectionTracking
 } = internalBinding('performance');
 
 const {
@@ -275,6 +276,8 @@ class PerformanceObserverEntryList {
   }
 }
 
+let gcTrackingIsEnabled = false;
+
 class PerformanceObserver extends AsyncResource {
   constructor(callback) {
     if (typeof callback !== 'function') {
@@ -336,6 +339,11 @@ class PerformanceObserver extends AsyncResource {
     if (entryTypes.length === 0) {
       throw new errors.ERR_VALID_PERFORMANCE_ENTRY_TYPE();
     }
+    if (entryTypes.includes(NODE_PERFORMANCE_ENTRY_TYPE_GC) &&
+      !gcTrackingIsEnabled) {
+      setupGarbageCollectionTracking();
+      gcTrackingIsEnabled = true;
+    }
     this.disconnect();
     this[kBuffer][kEntries] = [];
     L.init(this[kBuffer][kEntries]);

diff --git a/src/node_perf.cc b/src/node_perf.cc
@@ -296,8 +296,10 @@ void MarkGarbageCollectionEnd(Isolate* isolate,
                          entry);
 }
 
+static void SetupGarbageCollectionTracking(
+    const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
 
-inline void SetupGarbageCollectionTracking(Environment* env) {
   env->isolate()->AddGCPrologueCallback(MarkGarbageCollectionStart,
                                         static_cast<void*>(env));
   env->isolate()->AddGCEpilogueCallback(MarkGarbageCollectionEnd,
@@ -416,6 +418,8 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "markMilestone", MarkMilestone);
   env->SetMethod(target, "setupObservers", SetupPerformanceObservers);
   env->SetMethod(target, "timerify", Timerify);
+  env->SetMethod(
+      target, "setupGarbageCollectionTracking", SetupGarbageCollectionTracking);
 
   Local<Object> constants = Object::New(isolate);
 
@@ -452,8 +456,6 @@ void Initialize(Local<Object> target,
                             env->constants_string(),
                             constants,
                             attr).ToChecked();
-
-  SetupGarbageCollectionTracking(env);
 }
 
 }  // namespace performance