deps: cherry-pick garbage collection fixes from upstream V8

common.gypi

@@ -27,7 +27,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.4',
+    'v8_embedder_string': '-node.7',
 
     # Enable disassembler for `--print-code` v8 options
     'v8_enable_disassembler': 1,

deps/v8/src/heap/gc-tracer.cc

@@ -490,6 +490,8 @@ void GCTracer::PrintNVP() const {
           "promotion_rate=%.1f%% "
           "semi_space_copy_rate=%.1f%% "
           "new_space_allocation_throughput=%.1f "
+          "unmapper_chunks=%d "
+          "unmapper_delayed_chunks=%d "
           "context_disposal_rate=%.1f\n",
           duration, spent_in_mutator, current_.TypeName(true),
           current_.reduce_memory, current_.scopes[Scope::HEAP_PROLOGUE],
@@ -520,6 +522,8 @@ void GCTracer::PrintNVP() const {
           AverageSurvivalRatio(), heap_->promotion_rate_,
           heap_->semi_space_copied_rate_,
           NewSpaceAllocationThroughputInBytesPerMillisecond(),
+          heap_->memory_allocator()->unmapper()->NumberOfChunks(),
+          heap_->memory_allocator()->unmapper()->NumberOfDelayedChunks(),
           ContextDisposalRateInMilliseconds());
       break;
     case Event::MINOR_MARK_COMPACTOR:
@@ -654,6 +658,8 @@ void GCTracer::PrintNVP() const {
           "promotion_rate=%.1f%% "
           "semi_space_copy_rate=%.1f%% "
           "new_space_allocation_throughput=%.1f "
+          "unmapper_chunks=%d "
+          "unmapper_delayed_chunks=%d "
           "context_disposal_rate=%.1f "
           "compaction_speed=%.f\n",
           duration, spent_in_mutator, current_.TypeName(true),
@@ -731,6 +737,8 @@ void GCTracer::PrintNVP() const {
           AverageSurvivalRatio(), heap_->promotion_rate_,
           heap_->semi_space_copied_rate_,
           NewSpaceAllocationThroughputInBytesPerMillisecond(),
+          heap_->memory_allocator()->unmapper()->NumberOfChunks(),
+          heap_->memory_allocator()->unmapper()->NumberOfDelayedChunks(),
           ContextDisposalRateInMilliseconds(),
           CompactionSpeedInBytesPerMillisecond());
       break;

deps/v8/src/heap/heap.cc

@@ -1885,6 +1885,12 @@ void Heap::Scavenge() {
   IncrementalMarking::PauseBlackAllocationScope pause_black_allocation(
       incremental_marking());
 
+  if (mark_compact_collector()->sweeper().sweeping_in_progress() &&
+      memory_allocator_->unmapper()->NumberOfDelayedChunks() >
+          static_cast<int>(new_space_->MaximumCapacity() / Page::kPageSize)) {
+    mark_compact_collector()->EnsureSweepingCompleted();
+  }
+
   mark_compact_collector()->sweeper().EnsureNewSpaceCompleted();
 
   SetGCState(SCAVENGE);

deps/v8/src/heap/spaces.cc

@@ -408,6 +408,15 @@ void MemoryAllocator::Unmapper::ReconsiderDelayedChunks() {
   }
 }
 
+int MemoryAllocator::Unmapper::NumberOfChunks() {
+  base::LockGuard<base::Mutex> guard(&mutex_);
+  size_t result = 0;
+  for (int i = 0; i < kNumberOfChunkQueues; i++) {
+    result += chunks_[i].size();
+  }
+  return static_cast<int>(result);
+}
+
 bool MemoryAllocator::CanFreeMemoryChunk(MemoryChunk* chunk) {
   MarkCompactCollector* mc = isolate_->heap()->mark_compact_collector();
   // We cannot free a memory chunk in new space while the sweeper is running

deps/v8/src/heap/spaces.h

@@ -1199,6 +1199,13 @@ class V8_EXPORT_PRIVATE MemoryAllocator {
 
     bool has_delayed_chunks() { return delayed_regular_chunks_.size() > 0; }
 
+    int NumberOfDelayedChunks() {
+      base::LockGuard<base::Mutex> guard(&mutex_);
+      return static_cast<int>(delayed_regular_chunks_.size());
+    }
+
+    int NumberOfChunks();
+
    private:
     static const int kReservedQueueingSlots = 64;
     static const int kMaxUnmapperTasks = 24;