Bug 1125101 - Incrementalise compacting GC by zones r=terrence

js/src/gc/GCRuntime.h

@@ -923,18 +923,20 @@ class GCRuntime
     void sweepBackgroundThings(ZoneList &zones, LifoAlloc &freeBlocks, ThreadType threadType);
     void assertBackgroundSweepingFinished();
     bool shouldCompact();
+    IncrementalProgress beginCompactPhase();
     IncrementalProgress compactPhase(JS::gcreason::Reason reason);
+    void endCompactPhase(JS::gcreason::Reason reason);
     void sweepTypesAfterCompacting(Zone *zone);
     void sweepZoneAfterCompacting(Zone *zone);
-    ArenaHeader *relocateArenas(JS::gcreason::Reason reason);
+    bool relocateArenas(Zone *zone, JS::gcreason::Reason reason);
-    void updateAllCellPointersParallel(MovingTracer *trc);
+    void updateAllCellPointersParallel(MovingTracer *trc, Zone *zone);
-    void updateAllCellPointersSerial(MovingTracer *trc);
+    void updateAllCellPointersSerial(MovingTracer *trc, Zone *zone);
-    void updatePointersToRelocatedCells();
+    void updatePointersToRelocatedCells(Zone *zone);
-    void releaseRelocatedArenas(ArenaHeader *relocatedList);
+    void releaseRelocatedArenas();
-    void releaseRelocatedArenasWithoutUnlocking(ArenaHeader *relocatedList, const AutoLockGC& lock);
+    void releaseRelocatedArenasWithoutUnlocking(const AutoLockGC& lock);
 #ifdef DEBUG
-    void protectRelocatedArenas(ArenaHeader *relocatedList);
+    void protectRelocatedArenas();
-    void unprotectRelocatedArenas(ArenaHeader *relocatedList);
+    void unprotectRelocatedArenas();
 #endif
     void finishCollection(JS::gcreason::Reason reason);
 
@@ -1074,6 +1076,7 @@ class GCRuntime
 
     /* Singly linekd list of zones to be swept in the background. */
     ZoneList backgroundSweepZones;
+
     /*
      * Free LIFO blocks are transferred to this allocator before being freed on
      * the background GC thread.
@@ -1105,6 +1108,13 @@ class GCRuntime
      */
     js::gc::ArenaHeader *arenasAllocatedDuringSweep;
 
+    /*
+     * Incremental compacting state.
+     */
+    bool startedCompacting;
+    js::gc::ZoneList zonesToMaybeCompact;
+    ArenaHeader* relocatedArenasToRelease;
+
 #ifdef JS_GC_MARKING_VALIDATION
     js::gc::MarkingValidator *markingValidator;
 #endif
@@ -1239,9 +1249,6 @@ class GCRuntime
     int inUnsafeRegion;
 
     size_t noGCOrAllocationCheck;
-
-    ArenaHeader* relocatedArenasToRelease;
-
 #endif
 
     /* Synchronize GC heap access between main thread and GCHelperState. */

js/src/gc/Zone.cpp

@@ -384,3 +384,10 @@ ZoneList::removeFront()
 
     front->listNext_ = Zone::NotOnList;
 }
+
+void
+ZoneList::clear()
+{
+    while (!isEmpty())
+        removeFront();
+}

js/src/jsgc.cpp

@@ -1085,6 +1085,8 @@ GCRuntime::GCRuntime(JSRuntime *rt) :
     sweepKindIndex(0),
     abortSweepAfterCurrentGroup(false),
     arenasAllocatedDuringSweep(nullptr),
+    startedCompacting(false),
+    relocatedArenasToRelease(nullptr),
 #ifdef JS_GC_MARKING_VALIDATION
     markingValidator(nullptr),
 #endif
@@ -1113,7 +1115,6 @@ GCRuntime::GCRuntime(JSRuntime *rt) :
 #ifdef DEBUG
     inUnsafeRegion(0),
     noGCOrAllocationCheck(0),
-    relocatedArenasToRelease(nullptr),
 #endif
     lock(nullptr),
     lockOwner(nullptr),
@@ -2016,6 +2017,16 @@ RelocateArena(ArenaHeader *aheader)
             CrashAtUnhandlableOOM("Could not allocate new arena while compacting");
         }
     }
+
+#ifdef DEBUG
+    for (ArenaCellIterUnderFinalize i(aheader); !i.done(); i.next()) {
+        TenuredCell *src = i.getCell();
+        MOZ_ASSERT(RelocationOverlay::isCellForwarded(src));
+        TenuredCell *dest = Forwarded(src);
+        MOZ_ASSERT(src->isMarked(BLACK) == dest->isMarked(BLACK));
+        MOZ_ASSERT(src->isMarked(GRAY) == dest->isMarked(GRAY));
+    }
+#endif
 }
 
 /*
@@ -2114,26 +2125,38 @@ ArenaLists::relocateArenas(ArenaHeader *&relocatedListOut, JS::gcreason::Reason
     return true;
 }
 
-ArenaHeader *
+bool
-GCRuntime::relocateArenas(JS::gcreason::Reason reason)
+GCRuntime::relocateArenas(Zone *zone, JS::gcreason::Reason reason)
 {
     gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT_MOVE);
 
-    ArenaHeader *relocatedList = nullptr;
+    MOZ_ASSERT(!zone->isPreservingCode());
-    for (GCZonesIter zone(rt); !zone.done(); zone.next()) {
+    MOZ_ASSERT(CanRelocateZone(rt, zone));
-        MOZ_ASSERT(zone->isGCFinished());
-        MOZ_ASSERT(!zone->isPreservingCode());
 
-        if (CanRelocateZone(rt, zone)) {
+    jit::StopAllOffThreadCompilations(zone);
-            jit::StopAllOffThreadCompilations(zone);
+
-            if (zone->arenas.relocateArenas(relocatedList, reason, stats))
+    if (!zone->arenas.relocateArenas(relocatedArenasToRelease, reason, stats))
-                zone->setGCState(Zone::Compact);
+        return false;
+
+#ifdef DEBUG
+    // Check that we did as much compaction as we should have. There
+    // should always be less than one arena's worth of free cells.
+    for (ALL_ALLOC_KINDS(i)) {
+        size_t thingsPerArena = Arena::thingsPerArena(Arena::thingSize(i));
+        if (CanRelocateAllocKind(i)) {
+            ArenaList &al = zone->arenas.arenaLists[i];
+            size_t freeCells = 0;
+            for (ArenaHeader *arena = al.arenaAfterCursor(); arena; arena = arena->next)
+                freeCells += arena->countFreeCells();
+            MOZ_ASSERT(freeCells < thingsPerArena);
         }
     }
+#endif
 
-    return relocatedList;
+    return true;
 }
 
+
 void
 MovingTracer::Visit(JSTracer *jstrc, void **thingp, JSGCTraceKind kind)
 {
@@ -2267,7 +2290,7 @@ struct ArenasToUpdate
         BACKGROUND = 2,
         ALL = FOREGROUND | BACKGROUND
     };
-    ArenasToUpdate(JSRuntime *rt, KindsToUpdate kinds);
+    ArenasToUpdate(Zone *zone, KindsToUpdate kinds);
     bool done() { return initialized && arena == nullptr; }
     ArenaHeader* next(AutoLockHelperThreadState& lock);
     ArenaHeader *getArenasToUpdate(AutoLockHelperThreadState& lock, unsigned max);
@@ -2275,7 +2298,7 @@ struct ArenasToUpdate
   private:
     bool initialized;
     KindsToUpdate kinds;
-    GCZonesIter zone;    // Current zone to process, unless zone.done()
+    Zone *zone;          // Zone to process
     unsigned kind;       // Current alloc kind to process
     ArenaHeader *arena;  // Next arena to process
 
@@ -2299,9 +2322,10 @@ bool ArenasToUpdate::shouldProcessKind(AllocKind kind)
         return (kinds & FOREGROUND) != 0;
 }
 
-ArenasToUpdate::ArenasToUpdate(JSRuntime *rt, KindsToUpdate kinds)
+ArenasToUpdate::ArenasToUpdate(Zone *zone, KindsToUpdate kinds)
-  : initialized(false), kinds(kinds), zone(rt, SkipAtoms)
+  : initialized(false), kinds(kinds), zone(zone)
 {
+    MOZ_ASSERT(zone->isGCCompacting());
     MOZ_ASSERT(kinds && !(kinds & ~ALL));
 }
 
@@ -2320,33 +2344,30 @@ ArenasToUpdate::next(AutoLockHelperThreadState& lock)
     if (initialized) {
         MOZ_ASSERT(arena);
         MOZ_ASSERT(shouldProcessKind(AllocKind(kind)));
-        MOZ_ASSERT(!zone.done());
+        MOZ_ASSERT(zone);
         goto resumePoint;
     }
 
     initialized = true;
-    for (; !zone.done(); zone.next()) {
+    for (kind = 0; kind < size_t(AllocKind::LIMIT); ++kind) {
-        if (zone->isGCCompacting()) {
+        if (shouldProcessKind(AllocKind(kind))) {
-            for (kind = 0; kind < size_t(AllocKind::LIMIT); ++kind) {
+            for (arena = zone->arenas.getFirstArena(AllocKind(kind));
-                if (shouldProcessKind(AllocKind(kind))) {
+                 arena;
-                    for (arena = zone.get()->arenas.getFirstArena(AllocKind(kind));
+                 arena = arena->next)
-                         arena;
+            {
-                         arena = arena->next)
+                return arena;
-                    {
+              resumePoint:;
-                        return arena;
-                      resumePoint:;
-                    }
-                }
             }
         }
     }
+    zone = nullptr;
     return nullptr;
 }
 
 ArenaHeader *
 ArenasToUpdate::getArenasToUpdate(AutoLockHelperThreadState& lock, unsigned count)
 {
-    if (zone.done())
+    if (!zone)
         return nullptr;
 
     ArenaHeader *head = nullptr;
@@ -2432,7 +2453,7 @@ UpdateCellPointersTask::run()
 } // namespace js
 
 void
-GCRuntime::updateAllCellPointersParallel(MovingTracer *trc)
+GCRuntime::updateAllCellPointersParallel(MovingTracer *trc, Zone *zone)
 {
     AutoDisableProxyCheck noProxyCheck(rt); // These checks assert when run in parallel.
 
@@ -2443,8 +2464,8 @@ GCRuntime::updateAllCellPointersParallel(MovingTracer *trc)
     UpdateCellPointersTask bgTasks[maxTasks];
     UpdateCellPointersTask fgTask;
 
-    ArenasToUpdate fgArenas(rt, ArenasToUpdate::FOREGROUND);
+    ArenasToUpdate fgArenas(zone, ArenasToUpdate::FOREGROUND);
-    ArenasToUpdate bgArenas(rt, ArenasToUpdate::BACKGROUND);
+    ArenasToUpdate bgArenas(zone, ArenasToUpdate::BACKGROUND);
 
     unsigned tasksStarted = 0;
     {
@@ -2469,12 +2490,12 @@ GCRuntime::updateAllCellPointersParallel(MovingTracer *trc)
 }
 
 void
-GCRuntime::updateAllCellPointersSerial(MovingTracer *trc)
+GCRuntime::updateAllCellPointersSerial(MovingTracer *trc, Zone *zone)
 {
     UpdateCellPointersTask task;
     {
         AutoLockHelperThreadState lock;
-        ArenasToUpdate allArenas(rt, ArenasToUpdate::ALL);
+        ArenasToUpdate allArenas(zone, ArenasToUpdate::ALL);
         task.init(rt, &allArenas, lock);
     }
     task.runFromMainThread(rt);
@@ -2487,20 +2508,24 @@ GCRuntime::updateAllCellPointersSerial(MovingTracer *trc)
  * part of the traversal.
  */
 void
-GCRuntime::updatePointersToRelocatedCells()
+GCRuntime::updatePointersToRelocatedCells(Zone *zone)
 {
+    MOZ_ASSERT(zone->isGCCompacting());
     MOZ_ASSERT(rt->currentThreadHasExclusiveAccess());
 
     gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT_UPDATE);
     MovingTracer trc(rt);
 
     // Fixup compartment global pointers as these get accessed during marking.
-    for (GCCompartmentsIter comp(rt); !comp.done(); comp.next())
+    for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next())
         comp->fixupAfterMovingGC();
 
     // Fixup cross compartment wrappers as we assert the existence of wrappers in the map.
     for (CompartmentsIter comp(rt, SkipAtoms); !comp.done(); comp.next()) {
+        // Sweep the wrapper map to update its pointers.
         comp->sweepCrossCompartmentWrappers();
+
+        // Mark the contents of the map to update each wrapper's cross compartment pointer.
         comp->markCrossCompartmentWrappers(&trc);
     }
 
@@ -2508,9 +2533,9 @@ GCRuntime::updatePointersToRelocatedCells()
     // them. Since updating each cell is independent we try to parallelize this
     // as much as possible.
     if (CanUseExtraThreads())
-        updateAllCellPointersParallel(&trc);
+        updateAllCellPointersParallel(&trc, zone);
     else
-        updateAllCellPointersSerial(&trc);
+        updateAllCellPointersSerial(&trc, zone);
 
     // Mark roots to update them.
     {
@@ -2520,7 +2545,7 @@ GCRuntime::updatePointersToRelocatedCells()
         Debugger::markAll(&trc);
         Debugger::markIncomingCrossCompartmentEdges(&trc);
 
-        for (GCCompartmentsIter c(rt); !c.done(); c.next()) {
+        for (CompartmentsInZoneIter c(zone); !c.done(); c.next()) {
             WeakMapBase::markAll(c, &trc);
             if (c->watchpointMap)
                 c->watchpointMap->markAll(&trc);
@@ -2536,10 +2561,7 @@ GCRuntime::updatePointersToRelocatedCells()
     WatchpointMap::sweepAll(rt);
     Debugger::sweepAll(rt->defaultFreeOp());
     jit::JitRuntime::SweepJitcodeGlobalTable(rt);
-    for (GCZonesIter zone(rt); !zone.done(); zone.next()) {
+    rt->gc.sweepZoneAfterCompacting(zone);
-        if (zone->isGCCompacting())
-            rt->gc.sweepZoneAfterCompacting(zone);
-    }
 
     // Type inference may put more blocks here to free.
     freeLifoAlloc.freeAll();
@@ -2555,9 +2577,9 @@ GCRuntime::updatePointersToRelocatedCells()
 
 #ifdef DEBUG
 void
-GCRuntime::protectRelocatedArenas(ArenaHeader *relocatedList)
+GCRuntime::protectRelocatedArenas()
 {
-    for (ArenaHeader* arena = relocatedList, *next; arena; arena = next) {
+    for (ArenaHeader* arena = relocatedArenasToRelease, *next; arena; arena = next) {
         next = arena->next;
 #if defined(XP_WIN)
         DWORD oldProtect;
@@ -2571,9 +2593,9 @@ GCRuntime::protectRelocatedArenas(ArenaHeader *relocatedList)
 }
 
 void
-GCRuntime::unprotectRelocatedArenas(ArenaHeader *relocatedList)
+GCRuntime::unprotectRelocatedArenas()
 {
-    for (ArenaHeader* arena = relocatedList; arena; arena = arena->next) {
+    for (ArenaHeader* arena = relocatedArenasToRelease; arena; arena = arena->next) {
 #if defined(XP_WIN)
         DWORD oldProtect;
         if (!VirtualProtect(arena, ArenaSize, PAGE_READWRITE, &oldProtect))
@@ -2587,21 +2609,21 @@ GCRuntime::unprotectRelocatedArenas(ArenaHeader *relocatedList)
 #endif
 
 void
-GCRuntime::releaseRelocatedArenas(ArenaHeader *relocatedList)
+GCRuntime::releaseRelocatedArenas()
 {
     AutoLockGC lock(rt);
-    releaseRelocatedArenasWithoutUnlocking(relocatedList, lock);
+    releaseRelocatedArenasWithoutUnlocking(lock);
     expireChunksAndArenas(true, lock);
 }
 
 void
-GCRuntime::releaseRelocatedArenasWithoutUnlocking(ArenaHeader *relocatedList, const AutoLockGC &lock)
+GCRuntime::releaseRelocatedArenasWithoutUnlocking(const AutoLockGC &lock)
 {
     // Release the relocated arenas, now containing only forwarding pointers
     unsigned count = 0;
-    while (relocatedList) {
+    while (relocatedArenasToRelease) {
-        ArenaHeader *aheader = relocatedList;
+        ArenaHeader *aheader = relocatedArenasToRelease;
-        relocatedList = relocatedList->next;
+        relocatedArenasToRelease = relocatedArenasToRelease->next;
 
         // Clear the mark bits
         aheader->unmarkAll();
@@ -2631,9 +2653,8 @@ GCRuntime::releaseHeldRelocatedArenas()
     // In debug mode we don't release relocated arenas straight away.  Instead
     // we protect them and hold onto them until the next GC sweep phase to catch
     // any pointers to them that didn't get forwarded.
-    unprotectRelocatedArenas(relocatedArenasToRelease);
+    unprotectRelocatedArenas();
-    releaseRelocatedArenas(relocatedArenasToRelease);
+    releaseRelocatedArenas();
-    relocatedArenasToRelease = nullptr;
 #endif
 }
 
@@ -3191,7 +3212,6 @@ GCRuntime::assertBackgroundSweepingFinished()
 #ifdef DEBUG
     MOZ_ASSERT(backgroundSweepZones.isEmpty());
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
-        MOZ_ASSERT(!zone->isOnList());
         for (ALL_ALLOC_KINDS(i)) {
             MOZ_ASSERT(!zone->arenas.arenaListsToSweep[i]);
             MOZ_ASSERT(zone->arenas.doneBackgroundFinalize(i));
@@ -5266,7 +5286,7 @@ GCRuntime::endSweepPhase(bool lastGC)
 }
 
 GCRuntime::IncrementalProgress
-GCRuntime::compactPhase(JS::gcreason::Reason reason)
+GCRuntime::beginCompactPhase()
 {
     gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT);
 
@@ -5279,63 +5299,60 @@ GCRuntime::compactPhase(JS::gcreason::Reason reason)
         waitBackgroundSweepEnd();
     }
 
+    MOZ_ASSERT(zonesToMaybeCompact.isEmpty());
+    for (GCZonesIter zone(rt); !zone.done(); zone.next()) {
+        if (CanRelocateZone(rt, zone))
+            zonesToMaybeCompact.append(zone);
+    }
+
+    MOZ_ASSERT(!relocatedArenasToRelease);
+    startedCompacting = true;
+    return Finished;
+}
+
+GCRuntime::IncrementalProgress
+GCRuntime::compactPhase(JS::gcreason::Reason reason)
+{
     MOZ_ASSERT(rt->gc.nursery.isEmpty());
     assertBackgroundSweepingFinished();
+    MOZ_ASSERT(startedCompacting);
 
-    ArenaHeader *relocatedList = relocateArenas(reason);
+    gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT);
-    if (relocatedList)
-        updatePointersToRelocatedCells();
 
-#ifdef DEBUG
+    while (!zonesToMaybeCompact.isEmpty()) {
-    for (ArenaHeader *arena = relocatedList; arena; arena = arena->next) {
+        Zone *zone = zonesToMaybeCompact.front();
-        for (ArenaCellIterUnderFinalize i(arena); !i.done(); i.next()) {
+        MOZ_ASSERT(zone->isGCFinished());
-            TenuredCell *src = i.getCell();
+        if (relocateArenas(zone, reason)) {
-            MOZ_ASSERT(RelocationOverlay::isCellForwarded(src));
+            zone->setGCState(Zone::Compact);
-            TenuredCell *dest = Forwarded(src);
+            updatePointersToRelocatedCells(zone);
-            MOZ_ASSERT(src->isMarked(BLACK) == dest->isMarked(BLACK));
+            zone->setGCState(Zone::Finished);
-            MOZ_ASSERT(src->isMarked(GRAY) == dest->isMarked(GRAY));
         }
+        zonesToMaybeCompact.removeFront();
     }
-#endif
-
-    // Release the relocated arenas, or in debug builds queue them to be
-    // released until the start of the next GC unless this is the last GC or we
-    // are doing a last ditch GC.
-#ifndef DEBUG
-    releaseRelocatedArenas(relocatedList);
-#else
-    if (reason != JS::gcreason::DEBUG_GC) {
-        releaseRelocatedArenas(relocatedList);
-    } else {
-        MOZ_ASSERT(!relocatedArenasToRelease);
-        protectRelocatedArenas(relocatedList);
-        relocatedArenasToRelease = relocatedList;
-    }
-#endif
 
 #ifdef DEBUG
     CheckHashTablesAfterMovingGC(rt);
-    for (GCZonesIter zone(rt); !zone.done(); zone.next()) {
-        if (zone->isGCCompacting()) {
-            MOZ_ASSERT(!zone->isPreservingCode());
-            zone->arenas.checkEmptyFreeLists();
-
-            // Check that we did as much compaction as we should have. There
-            // should always be less than one arena's worth of free cells.
-            for (ALL_ALLOC_KINDS(i)) {
-                size_t thingsPerArena = Arena::thingsPerArena(Arena::thingSize(i));
-                if (CanRelocateAllocKind(i)) {
-                    ArenaList &al = zone->arenas.arenaLists[i];
-                    size_t freeCells = 0;
-                    for (ArenaHeader *arena = al.arenaAfterCursor(); arena; arena = arena->next)
-                        freeCells += arena->countFreeCells();
-                    MOZ_ASSERT(freeCells < thingsPerArena);
-                }
-            }
-        }
-    }
 #endif
-    return Finished;
+
+    return zonesToMaybeCompact.isEmpty() ? Finished : NotFinished;
+}
+
+void
+GCRuntime::endCompactPhase(JS::gcreason::Reason reason)
+{
+    // Release the relocated arenas, or in debug builds queue them to be
+    // released at the start of the next GC unless this is the last GC or we are
+    // doing a last ditch GC.
+#ifndef DEBUG
+    releaseRelocatedArenas();
+#else
+    if (reason != JS::gcreason::DEBUG_GC)
+        releaseRelocatedArenas();
+    else
+        protectRelocatedArenas();
+#endif
+
+    startedCompacting = false;
 }
 
 void
@@ -5349,7 +5366,7 @@ GCRuntime::finishCollection(JS::gcreason::Reason reason)
 
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
         if (zone->isCollecting()) {
-            MOZ_ASSERT(zone->isGCFinished() || zone->isGCCompacting());
+            MOZ_ASSERT(zone->isGCFinished());
             zone->setGCState(Zone::NoGC);
             zone->active = false;
         }
@@ -5358,6 +5375,8 @@ GCRuntime::finishCollection(JS::gcreason::Reason reason)
         MOZ_ASSERT(!zone->wasGCStarted());
     }
 
+    MOZ_ASSERT(zonesToMaybeCompact.isEmpty());
+
     if (invocationKind == GC_SHRINK) {
         // Ensure excess chunks are returns to the system and free arenas
         // decommitted.
@@ -5517,7 +5536,10 @@ GCRuntime::resetIncrementalGC(const char *reason)
         }
 
         bool wasCompacting = isCompacting;
-        isCompacting = false;
+
+        isCompacting = true;
+        startedCompacting = true;
+        zonesToMaybeCompact.clear();
 
         SliceBudget budget;
         incrementalCollectSlice(budget, JS::gcreason::RESET);
@@ -5533,11 +5555,13 @@ GCRuntime::resetIncrementalGC(const char *reason)
     stats.reset(reason);
 
 #ifdef DEBUG
+    assertBackgroundSweepingFinished();
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
+        MOZ_ASSERT(!zone->isCollecting());
         MOZ_ASSERT(!zone->needsIncrementalBarrier());
-        for (ALL_ALLOC_KINDS(i))
+        MOZ_ASSERT(!zone->isOnList());
-            MOZ_ASSERT(!zone->arenas.arenaListsToSweep[i]);
     }
+    MOZ_ASSERT(zonesToMaybeCompact.isEmpty());
 #endif
 }
 
@@ -5735,14 +5759,22 @@ GCRuntime::incrementalCollectSlice(SliceBudget &budget, JS::gcreason::Reason rea
         endSweepPhase(lastGC);
 
         incrementalState = COMPACT;
+        MOZ_ASSERT(!startedCompacting);
 
         /* Yield before compacting since it is not incremental. */
         if (isCompacting && isIncremental)
             break;
 
       case COMPACT:
-        if (isCompacting && compactPhase(reason) == NotFinished)
+        if (isCompacting) {
-            break;
+            if (!startedCompacting && beginCompactPhase() == NotFinished)
+                break;
+
+            if (compactPhase(reason) == NotFinished)
+                break;
+
+            endCompactPhase(reason);
+        }
 
         finishCollection(reason);
 
@@ -6205,12 +6237,11 @@ GCRuntime::onOutOfMallocMemory()
 void
 GCRuntime::onOutOfMallocMemory(const AutoLockGC &lock)
 {
+#ifdef DEBUG
     // Release any relocated arenas we may be holding on to, without releasing
     // the GC lock.
-#ifdef DEBUG
+    unprotectRelocatedArenas();
-    unprotectRelocatedArenas(relocatedArenasToRelease);
+    releaseRelocatedArenasWithoutUnlocking(lock);
-    releaseRelocatedArenasWithoutUnlocking(relocatedArenasToRelease, lock);
-    relocatedArenasToRelease = nullptr;
 #endif
 
     // Throw away any excess chunks we have lying around.

js/src/jsgc.h

@@ -1382,6 +1382,7 @@ class ZoneList
     void append(Zone *zone);
     void transferFrom(ZoneList &other);
     void removeFront();
+    void clear();
 
   private:
     explicit ZoneList(Zone *singleZone);