Bug 1661293 - Move idle-time nursery GCs to a new nsJSContext::MaybePokeGC r=jonco,smaug

Differential Revision: https://phabricator.services.mozilla.com/D100367

dom/base/CCGCScheduler.cpp

@@ -465,6 +465,9 @@ void CCGCScheduler::PokeFullGC() {
 
 void CCGCScheduler::PokeGC(JS::GCReason aReason, JSObject* aObj,
                            TimeDuration aDelay) {
+  MOZ_ASSERT(aReason != JS::GCReason::NO_REASON);
+  MOZ_ASSERT(aReason != JS::GCReason::EAGER_NURSERY_COLLECTION);
+
   if (mDidShutdown) {
     return;
   }
@@ -502,6 +505,24 @@ void CCGCScheduler::PokeGC(JS::GCReason aReason, JSObject* aObj,
   EnsureGCRunner(delay);
 }
 
+void CCGCScheduler::PokeMinorGC(JS::GCReason aReason) {
+  MOZ_ASSERT(aReason != JS::GCReason::NO_REASON);
+
+  if (mDidShutdown) {
+    return;
+  }
+
+  SetWantEagerMinorGC(aReason);
+
+  if (mGCRunner || mHaveAskedParent || mCCRunner) {
+    // There's already a runner, or there will be, so just return.
+    return;
+  }
+
+  // Immediately start looking for idle time to run the minor GC.
+  EnsureGCRunner(0);
+}
+
 void CCGCScheduler::EnsureGCRunner(TimeDuration aDelay) {
   if (mGCRunner) {
     return;

dom/base/CCGCScheduler.h

@@ -168,6 +168,7 @@ class CCGCScheduler {
   void PokeShrinkingGC();
   void PokeFullGC();
   void MaybePokeCC(TimeStamp aNow, uint32_t aSuspectedCCObjects);
+  void PokeMinorGC(JS::GCReason aReason);
 
   void UserIsInactive();
   void UserIsActive();

dom/base/nsJSEnvironment.cpp

@@ -1655,6 +1655,17 @@ void nsJSContext::PokeGC(JS::GCReason aReason, JSObject* aObj,
 }
 
 // static
+void nsJSContext::MaybePokeGC() {
+  if (sShuttingDown) {
+    return;
+  }
+
+  JSRuntime* rt = CycleCollectedJSRuntime::Get()->Runtime();
+  if (JS::IsIdleGCTaskNeeded(rt)) {
+    sScheduler.PokeMinorGC(JS::GCReason::EAGER_NURSERY_COLLECTION);
+  }
+}
+
 void nsJSContext::DoLowMemoryGC() {
   if (sShuttingDown) {
     return;

dom/base/nsJSEnvironment.h

@@ -103,10 +103,15 @@ class nsJSContext : public nsIScriptContext {
   static void MaybeRunNextCollectorSlice(nsIDocShell* aDocShell,
                                          JS::GCReason aReason);
 
-  // The GC should probably run soon, in the zone of object aObj (if given).
+  // The GC should run soon, in the zone of aObj if given. If aObj is
+  // nullptr, collect all Zones.
   static void PokeGC(JS::GCReason aReason, JSObject* aObj,
                      mozilla::TimeDuration aDelay = 0);
 
+  // If usage is nearing a threshold, request idle-only GC work. (This is called
+  // when a collection would be relatively convenient.)
+  static void MaybePokeGC();
+
   // Immediately perform a non-incremental shrinking GC and CC.
   static void DoLowMemoryGC();
 

js/xpconnect/src/XPCJSContext.cpp

@@ -38,6 +38,7 @@
 #include "nsCCUncollectableMarker.h"
 #include "nsCycleCollectionNoteRootCallback.h"
 #include "nsCycleCollector.h"
+#include "nsJSEnvironment.h"
 #include "jsapi.h"
 #include "js/ArrayBuffer.h"
 #include "js/ContextOptions.h"
@@ -1490,6 +1491,8 @@ void XPCJSContext::AfterProcessTask(uint32_t aNewRecursionDepth) {
   SetPendingException(nullptr);
 }
 
+void XPCJSContext::MaybePokeGC() { nsJSContext::MaybePokeGC(); }
+
 bool XPCJSContext::IsSystemCaller() const {
   return nsContentUtils::IsSystemCaller(Context());
 }

js/xpconnect/src/xpcprivate.h

@@ -337,6 +337,10 @@ class XPCJSContext final : public mozilla::CycleCollectedJSContext,
   virtual void BeforeProcessTask(bool aMightBlock) override;
   virtual void AfterProcessTask(uint32_t aNewRecursionDepth) override;
 
+  // Relay to the CCGCScheduler instead of queuing up an idle runnable
+  // (as is done for workers in CycleCollectedJSContext).
+  virtual void MaybePokeGC() override;
+
   ~XPCJSContext();
 
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf);

xpcom/base/CycleCollectedJSContext.cpp

@@ -467,7 +467,7 @@ void CycleCollectedJSContext::AfterProcessTask(uint32_t aRecursionDepth) {
 
   // This should be a fast test so that it won't affect the next task
   // processing.
-  IsIdleGCTaskNeeded();
+  MaybePokeGC();
 }
 
 void CycleCollectedJSContext::AfterProcessMicrotasks() {
@@ -493,7 +493,9 @@ void CycleCollectedJSContext::AfterProcessMicrotasks() {
   JS::ClearKeptObjects(mJSContext);
 }
 
-void CycleCollectedJSContext::IsIdleGCTaskNeeded() const {
+void CycleCollectedJSContext::MaybePokeGC() {
+  // Worker-compatible check to see if we want to do an idle-time minor
+  // GC.
   class IdleTimeGCTaskRunnable : public mozilla::IdleRunnable {
    public:
     using mozilla::IdleRunnable::IdleRunnable;

xpcom/base/CycleCollectedJSContext.h

@@ -210,8 +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 GC task.
-  void IsIdleGCTaskNeeded() const;
+  // Check whether we need an idle minor GC task.
+  virtual void MaybePokeGC();
 
   uint32_t RecursionDepth() const;