Commit 2c04e31b authored by Jon Coppeard's avatar Jon Coppeard
Browse files

Bug 1425450 - Only trace JS holders in collecting zones r=mccr8 

Now that we have some per-zone vectors we can skip tracing those for zones that are not being collected.

Differential Revision: https://phabricator.services.mozilla.com/D68523

--HG--
extra : moz-landing-system : lando
parent 368614f7

js/public/GCAPI.h

+2 −0
Original line number Diff line number Diff line
@@ -1114,6 +1114,8 @@ extern JS_PUBLIC_API void SetHostCleanupFinalizationRegistryCallback( 
 */

extern JS_PUBLIC_API void ClearKeptObjects(JSContext* cx);



extern JS_PUBLIC_API bool ZoneIsCollecting(Zone* zone);



}  // namespace JS



namespace js {

js/src/jsapi.cpp

+4 −0
Original line number Diff line number Diff line
@@ -1373,6 +1373,10 @@ JS_PUBLIC_API void JS::ClearKeptObjects(JSContext* cx) { 
  }

}



JS_PUBLIC_API bool JS::ZoneIsCollecting(JS::Zone* zone) {

  return zone->wasGCStarted();

}



JS_PUBLIC_API bool JS_AddWeakPointerZonesCallback(JSContext* cx,

                                                  JSWeakPointerZonesCallback cb,

                                                  void* data) {

xpcom/base/CycleCollectedJSRuntime.cpp

+25 −16
Original line number Diff line number Diff line
@@ -15,26 +15,25 @@ 
//    and any cycle they participate in is uncollectable. These roots are

//    traced from TraceNativeBlackRoots.

//

// 3. all other roots held by C++ objects that participate in cycle

//    collection, held by us (see TraceNativeGrayRoots). Roots from this

//    category are considered grey in the cycle collector; whether or not

//    they are collected depends on the objects that hold them.

// 3. all other roots held by C++ objects that participate in cycle collection,

//    held by us (see TraceNativeGrayRoots). Roots from this category are

//    considered grey in the cycle collector; whether or not they are collected

//    depends on the objects that hold them.

//

// Note that if a root is in multiple categories the fact that it is in

// category 1 or 2 that takes precedence, so it will be considered black.

//

// During garbage collection we switch to an additional mark color (gray)

// when tracing inside TraceNativeGrayRoots. This allows us to walk those

// roots later on and add all objects reachable only from them to the

// cycle collector.

// During garbage collection we switch to an additional mark color (gray) when

// tracing inside TraceNativeGrayRoots. This allows us to walk those roots later

// on and add all objects reachable only from them to the cycle collector.

//

// Phases:

//

// 1. marking of the roots in category 1 by having the JS GC do its marking

// 2. marking of the roots in category 2 by having the JS GC call us back

//    (via JS_SetExtraGCRootsTracer) and running TraceNativeBlackRoots

// 3. marking of the roots in category 3 by TraceNativeGrayRoots using an

//    additional color (gray).

// 3. marking of the roots in category 3 by

//    TraceNativeGrayRootsInCollectingZones using an additional color (gray).

// 4. end of GC, GC can sweep its heap

//

// At some later point, when the cycle collector runs:
@@ -62,6 +61,7 @@ 
#include "GeckoProfiler.h"

#include "js/Debug.h"

#include "js/GCAPI.h"

#include "js/HeapAPI.h"

#include "js/Warnings.h"  // JS::SetWarningReporter

#include "jsfriendapi.h"

#include "mozilla/ArrayUtils.h"
@@ -490,9 +490,16 @@ JSHolderMap::Entry::Entry(void* aHolder, nsScriptObjectTracer* aTracer, 
JSHolderMap::JSHolderMap() : mJSHolderMap(256) {}



template <typename F>

inline void JSHolderMap::ForEach(F&& f) {

inline void JSHolderMap::ForEach(F&& f, WhichHolders aWhich) {

  // Multi-zone JS holders must always be considered.

  ForEach(mAnyZoneJSHolders, f, nullptr);



  for (auto i = mPerZoneJSHolders.modIter(); !i.done(); i.next()) {

    if (aWhich == HoldersInCollectingZones &&

        !JS::ZoneIsCollecting(i.get().key())) {

      continue;

    }



    EntryVector* holders = i.get().value().get();

    ForEach(*holders, f, i.get().key());

    if (holders->IsEmpty()) {
@@ -512,7 +519,7 @@ inline void JSHolderMap::ForEach(EntryVector& aJSHolders, const F& f, 
      break;  // Removed the last entry.

    }



    MOZ_ASSERT(entry->mZone == aZone);

    MOZ_ASSERT_IF(aZone, entry->mZone == aZone);

    f(entry->mHolder, entry->mTracer, aZone);

  }

}
@@ -725,7 +732,7 @@ void CycleCollectedJSRuntime::Shutdown(JSContext* cx) { 
#ifdef NS_BUILD_REFCNT_LOGGING

  JSLeakTracer tracer(Runtime());

  TraceNativeBlackRoots(&tracer);

  TraceNativeGrayRoots(&tracer);

  TraceNativeGrayRoots(&tracer, JSHolderMap::AllHolders);

#endif



#ifdef DEBUG
@@ -964,7 +971,7 @@ void CycleCollectedJSRuntime::TraceGrayJS(JSTracer* aTracer, void* aData) { 
  CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);



  // Mark these roots as gray so the CC can walk them later.

  self->TraceNativeGrayRoots(aTracer);

  self->TraceNativeGrayRoots(aTracer, JSHolderMap::HoldersInCollectingZones);

}



/* static */
@@ -1267,7 +1274,8 @@ static inline void CheckHolderIsSingleZone( 


#endif



void CycleCollectedJSRuntime::TraceNativeGrayRoots(JSTracer* aTracer) {

void CycleCollectedJSRuntime::TraceNativeGrayRoots(

    JSTracer* aTracer, JSHolderMap::WhichHolders aWhich) {

  // NB: This is here just to preserve the existing XPConnect order. I doubt it

  // would hurt to do this after the JS holders.

  TraceAdditionalNativeGrayRoots(aTracer);
@@ -1280,7 +1288,8 @@ void CycleCollectedJSRuntime::TraceNativeGrayRoots(JSTracer* aTracer) { 
        }

#endif

        tracer->Trace(holder, JsGcTracer(), aTracer);

      });

      },

      aWhich);

}



void CycleCollectedJSRuntime::AddJSHolder(void* aHolder,

xpcom/base/CycleCollectedJSRuntime.h

+6 −2
Original line number Diff line number Diff line
@@ -90,10 +90,13 @@ class IncrementalFinalizeRunnable; 
// SegmentedVector to speed up iteration.

class JSHolderMap {

 public:

  enum WhichHolders { AllHolders, HoldersInCollectingZones };



  JSHolderMap();



  // Call functor |f| for each holder.

  template <typename F>

  void ForEach(F&& f);

  void ForEach(F&& f, WhichHolders aWhich = AllHolders);



  bool Has(void* aHolder) const;

  nsScriptObjectTracer* Get(void* aHolder) const;
@@ -216,7 +219,8 @@ class CycleCollectedJSRuntime { 
  static void AfterWaitCallback(void* aCookie);



  virtual void TraceNativeBlackRoots(JSTracer* aTracer){};

  void TraceNativeGrayRoots(JSTracer* aTracer);

  void TraceNativeGrayRoots(JSTracer* aTracer,

                            JSHolderMap::WhichHolders aWhich);



 public:

  void FinalizeDeferredThings(