Bug 1661293 - Make nsJSContext::MaybePokeGC trigger EAGER_ALLOC_TRIGGER major GCs instead of just eager minor GCs r=jonco,smaug

Differential Revision: https://phabricator.services.mozilla.com/D100368

dom/base/nsJSEnvironment.cpp

@@ -1661,8 +1661,14 @@ void nsJSContext::MaybePokeGC() {
   }
 
   JSRuntime* rt = CycleCollectedJSRuntime::Get()->Runtime();
-  if (JS::IsIdleGCTaskNeeded(rt)) {
-    sScheduler.PokeMinorGC(JS::GCReason::EAGER_NURSERY_COLLECTION);
+  JS::GCReason reason = JS::WantEagerMinorGC(rt);
+  if (reason != JS::GCReason::NO_REASON) {
+    MOZ_ASSERT(reason == JS::GCReason::EAGER_NURSERY_COLLECTION);
+    sScheduler.PokeMinorGC(reason);
+  }
+  reason = JS::WantEagerMajorGC(rt);
+  if (reason != JS::GCReason::NO_REASON) {
+    PokeGC(reason, nullptr, 0);
   }
 }
 

js/public/GCAPI.h

@@ -1237,7 +1237,9 @@ JS_GetExternalStringCallbacks(JSString* str);
 
 namespace JS {
 
-extern JS_PUBLIC_API bool IsIdleGCTaskNeeded(JSRuntime* rt);
+extern JS_PUBLIC_API GCReason WantEagerMinorGC(JSRuntime* rt);
+
+extern JS_PUBLIC_API GCReason WantEagerMajorGC(JSRuntime* rt);
 
 extern JS_PUBLIC_API void MaybeRunNurseryCollection(JSRuntime* rt,
                                                     JS::GCReason reason);

js/src/gc/GC.cpp

@@ -1654,6 +1654,33 @@ void GCRuntime::maybeGC() {
   }
 }
 
+JS::GCReason GCRuntime::wantMajorGC() {
+  MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
+
+  // This implementation parallels maybeGC() above.
+
+  // From gcIfRequested().
+  if (majorGCRequested()) {
+    return majorGCTriggerReason;
+  }
+
+  if (isIncrementalGCInProgress()) {
+    return JS::GCReason::NO_REASON;
+  }
+
+  JS::GCReason reason = JS::GCReason::NO_REASON;
+  for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
+    if (checkEagerAllocTrigger(zone->gcHeapSize, zone->gcHeapThreshold) ||
+        checkEagerAllocTrigger(zone->mallocHeapSize,
+                               zone->mallocHeapThreshold)) {
+      zone->scheduleGC();
+      reason = JS::GCReason::EAGER_ALLOC_TRIGGER;
+    }
+  }
+
+  return reason;
+}
+
 bool GCRuntime::checkEagerAllocTrigger(const HeapSize& size,
                                        const HeapThreshold& threshold) {
   double thresholdBytes =

js/src/gc/GCRuntime.h

@@ -330,6 +330,7 @@ class GCRuntime {
   bool triggerZoneGC(Zone* zone, JS::GCReason reason, size_t usedBytes,
                      size_t thresholdBytes);
   void maybeGC();
+  JS::GCReason wantMajorGC();
   bool checkEagerAllocTrigger(const HeapSize& size,
                               const HeapThreshold& threshold);
   // The return value indicates whether a major GC was performed.

js/src/jsapi.cpp

@@ -1279,9 +1279,15 @@ JS_PUBLIC_API void JS_RemoveExtraGCRootsTracer(JSContext* cx,
   return cx->runtime()->gc.removeBlackRootsTracer(traceOp, data);
 }
 
-JS_PUBLIC_API bool JS::IsIdleGCTaskNeeded(JSRuntime* rt) {
-  // Currently, we only collect nursery during idle time.
-  return rt->gc.nursery().shouldCollect();
+JS_PUBLIC_API JS::GCReason JS::WantEagerMinorGC(JSRuntime* rt) {
+  if (rt->gc.nursery().shouldCollect()) {
+    return JS::GCReason::EAGER_NURSERY_COLLECTION;
+  }
+  return JS::GCReason::NO_REASON;
+}
+
+JS_PUBLIC_API JS::GCReason JS::WantEagerMajorGC(JSRuntime* rt) {
+  return rt->gc.wantMajorGC();
 }
 
 JS_PUBLIC_API void JS::MaybeRunNurseryCollection(JSRuntime* rt,

xpcom/base/CycleCollectedJSContext.h

@@ -210,7 +210,8 @@ class CycleCollectedJSContext : dom::PerThreadAtomCache, private JS::JobQueue {
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
   virtual void AfterProcessTask(uint32_t aRecursionDepth);
 
-  // Check whether we need an idle minor GC task.
+  // Check whether any eager thresholds have been reached, which would mean
+  // an idle GC task (minor or major) would be useful.
   virtual void MaybePokeGC();
 
   uint32_t RecursionDepth() const;

xpcom/base/CycleCollectedJSRuntime.h

@@ -376,7 +376,7 @@ class CycleCollectedJSRuntime {
 
   bool IsIdleGCTaskNeeded() {
     return !HasPendingIdleGCTask() && Runtime() &&
-           JS::IsIdleGCTaskNeeded(Runtime());
+           JS::WantEagerMinorGC(Runtime()) != JS::GCReason::NO_REASON;
   }
 
  public: