[heap] Introduce PromoteYoungGenerationGC

This CL separates logic for promoting all of new space during fast
promotion out of the heap and into a new dedicated
PromoteYoungGenerationGC class.

It currently assumes SemiSpaceNewSpace and will need to be extended with
support for PagedNewSpace.

Bug: v8:12612
Change-Id: I0e65c034b444634a31b3c00df0a4b558612f023f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3644610
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80492}

BUILD.bazel

@@ -1502,6 +1502,8 @@ filegroup(
         "src/heap/parallel-work-item.h",
         "src/heap/parked-scope.h",
         "src/heap/progress-bar.h",
+        "src/heap/promote-young-generation.cc",
+        "src/heap/promote-young-generation.h",
         "src/heap/read-only-heap-inl.h",
         "src/heap/read-only-heap.cc",
         "src/heap/read-only-heap.h",

BUILD.gn

@@ -3069,6 +3069,7 @@ v8_header_set("v8_internal_headers") {
     "src/heap/parallel-work-item.h",
     "src/heap/parked-scope.h",
     "src/heap/progress-bar.h",
+    "src/heap/promote-young-generation.h",
     "src/heap/read-only-heap-inl.h",
     "src/heap/read-only-heap.h",
     "src/heap/read-only-spaces.h",
@@ -4329,6 +4330,7 @@ v8_source_set("v8_base_without_compiler") {
     "src/heap/object-stats.cc",
     "src/heap/objects-visiting.cc",
     "src/heap/paged-spaces.cc",
+    "src/heap/promote-young-generation.cc",
     "src/heap/read-only-heap.cc",
     "src/heap/read-only-spaces.cc",
     "src/heap/safepoint.cc",

src/heap/heap.cc

@@ -70,6 +70,7 @@
 #include "src/heap/objects-visiting.h"
 #include "src/heap/paged-spaces-inl.h"
 #include "src/heap/parked-scope.h"
+#include "src/heap/promote-young-generation.h"
 #include "src/heap/read-only-heap.h"
 #include "src/heap/remembered-set.h"
 #include "src/heap/safepoint.h"
@@ -2298,16 +2299,15 @@ size_t Heap::PerformGarbageCollection(
   size_t start_young_generation_size =
       NewSpaceSize() + (new_lo_space() ? new_lo_space()->SizeOfObjects() : 0);
 
-  switch (collector) {
-    case GarbageCollector::MARK_COMPACTOR:
-      MarkCompact();
-      break;
-    case GarbageCollector::MINOR_MARK_COMPACTOR:
-      MinorMarkCompact();
-      break;
-    case GarbageCollector::SCAVENGER:
-      Scavenge();
-      break;
+  if (collector == GarbageCollector::MARK_COMPACTOR) {
+    MarkCompact();
+  } else if (fast_promotion_mode_ && CanPromoteYoungAndExpandOldGeneration(0)) {
+    PromoteYoungGeneration();
+  } else if (collector == GarbageCollector::MINOR_MARK_COMPACTOR) {
+    MinorMarkCompact();
+  } else {
+    DCHECK_EQ(GarbageCollector::SCAVENGER, collector);
+    Scavenge();
   }
 
   ProcessPretenuringFeedback();
@@ -2683,58 +2683,10 @@ void Heap::CheckNewSpaceExpansionCriteria() {
   new_lo_space()->SetCapacity(new_space()->Capacity());
 }
 
-void Heap::EvacuateYoungGeneration() {
-  TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_FAST_PROMOTE);
-  base::MutexGuard guard(relocation_mutex());
-  // Young generation garbage collection is orthogonal from full GC marking. It
-  // is possible that objects that are currently being processed for marking are
-  // reclaimed in the young generation GC that interleaves concurrent marking.
-  // Pause concurrent markers to allow processing them using
-  // `UpdateMarkingWorklistAfterYoungGenGC()`.
-  ConcurrentMarking::PauseScope pause_js_marking(concurrent_marking());
-  CppHeap::PauseConcurrentMarkingScope pause_cpp_marking(
-      CppHeap::From(cpp_heap_));
-  if (!FLAG_concurrent_marking) {
-    DCHECK(fast_promotion_mode_);
-    DCHECK(CanPromoteYoungAndExpandOldGeneration(0));
-  }
-
-  SemiSpaceNewSpace* semi_space_new_space =
-      SemiSpaceNewSpace::From(new_space());
-  // Move pages from new->old generation.
-  PageRange range(semi_space_new_space->first_allocatable_address(),
-                  semi_space_new_space->top());
-  for (auto it = range.begin(); it != range.end();) {
-    Page* p = (*++it)->prev_page();
-    semi_space_new_space->from_space().RemovePage(p);
-    Page::ConvertNewToOld(p);
-    if (incremental_marking()->IsMarking())
-      mark_compact_collector()->RecordLiveSlotsOnPage(p);
-  }
-
-  // Reset new space.
-  if (!semi_space_new_space->Rebalance()) {
-    FatalProcessOutOfMemory("NewSpace::Rebalance");
-  }
-  semi_space_new_space->ResetLinearAllocationArea();
-  semi_space_new_space->set_age_mark(semi_space_new_space->top());
-
-  for (auto it = new_lo_space()->begin(); it != new_lo_space()->end();) {
-    LargePage* page = *it;
-    // Increment has to happen after we save the page, because it is going to
-    // be removed below.
-    it++;
-    lo_space()->PromoteNewLargeObject(page);
-  }
-
-  // Fix up special trackers.
-  external_string_table_.PromoteYoung();
-  // GlobalHandles are updated in PostGarbageCollectonProcessing
-
-  size_t promoted = new_space()->Size() + new_lo_space()->Size();
-  IncrementYoungSurvivorsCounter(promoted);
-  IncrementPromotedObjectsSize(promoted);
-  IncrementSemiSpaceCopiedObjectSize(0);
+void Heap::PromoteYoungGeneration() {
+  tracer()->NotifyYoungGenerationHandling(
+      YoungGenerationHandling::kFastPromotionDuringScavenge);
+  promote_young_generation_gc_->EvacuateYoungGeneration();
 }
 
 void Heap::Scavenge() {
@@ -2746,12 +2698,6 @@ void Heap::Scavenge() {
         "[IncrementalMarking] Scavenge during marking.\n");
   }
 
-  if (fast_promotion_mode_ && CanPromoteYoungAndExpandOldGeneration(0)) {
-    tracer()->NotifyYoungGenerationHandling(
-        YoungGenerationHandling::kFastPromotionDuringScavenge);
-    EvacuateYoungGeneration();
-    return;
-  }
   tracer()->NotifyYoungGenerationHandling(
       YoungGenerationHandling::kRegularScavenge);
 
@@ -5762,6 +5708,7 @@ void Heap::SetUp(LocalHeap* main_thread_local_heap) {
   mark_compact_collector_.reset(new MarkCompactCollector(this));
 
   scavenger_collector_.reset(new ScavengerCollector(this));
+  promote_young_generation_gc_.reset(new PromoteYoungGenerationGC(this));
   minor_mark_compact_collector_.reset(new MinorMarkCompactCollector(this));
 
   incremental_marking_.reset(
@@ -6168,6 +6115,7 @@ void Heap::TearDown() {
   }
 
   scavenger_collector_.reset();
+  promote_young_generation_gc_.reset();
   array_buffer_sweeper_.reset();
   incremental_marking_.reset();
   concurrent_marking_.reset();

src/heap/heap.h

@@ -109,6 +109,7 @@ class ObjectIterator;
 class ObjectStats;
 class Page;
 class PagedSpace;
+class PromoteYoungGenerationGC;
 class ReadOnlyHeap;
 class RootVisitor;
 class RwxMemoryWriteScope;
@@ -1941,7 +1942,7 @@ class Heap {
 
   // Performs a minor collection in new generation.
   void Scavenge();
-  void EvacuateYoungGeneration();
+  void PromoteYoungGeneration();
 
   void UpdateYoungReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
@@ -2324,6 +2325,7 @@ class Heap {
   std::unique_ptr<MarkCompactCollector> mark_compact_collector_;
   std::unique_ptr<MinorMarkCompactCollector> minor_mark_compact_collector_;
   std::unique_ptr<ScavengerCollector> scavenger_collector_;
+  std::unique_ptr<PromoteYoungGenerationGC> promote_young_generation_gc_;
   std::unique_ptr<ArrayBufferSweeper> array_buffer_sweeper_;
 
   std::unique_ptr<MemoryAllocator> memory_allocator_;
@@ -2487,6 +2489,7 @@ class Heap {
   friend class ObjectStatsCollector;
   friend class Page;
   friend class PagedSpace;
+  friend class PromoteYoungGenerationGC;
   friend class ReadOnlyRoots;
   friend class Scavenger;
   friend class ScavengerCollector;

src/heap/promote-young-generation.cc

@@ -0,0 +1,76 @@
+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/promote-young-generation.h"
+
+#include "src/heap/concurrent-marking.h"
+#include "src/heap/cppgc-js/cpp-heap.h"
+#include "src/heap/gc-tracer-inl.h"
+#include "src/heap/heap.h"
+#include "src/heap/incremental-marking.h"
+#include "src/heap/large-spaces.h"
+#include "src/heap/mark-compact.h"
+#include "src/heap/new-spaces.h"
+#include "src/heap/paged-spaces-inl.h"
+
+namespace v8 {
+namespace internal {
+
+void PromoteYoungGenerationGC::EvacuateYoungGeneration() {
+  TRACE_GC(heap_->tracer(), GCTracer::Scope::SCAVENGER_FAST_PROMOTE);
+  base::MutexGuard guard(heap_->relocation_mutex());
+  // Young generation garbage collection is orthogonal from full GC marking. It
+  // is possible that objects that are currently being processed for marking are
+  // reclaimed in the young generation GC that interleaves concurrent marking.
+  // Pause concurrent markers to allow processing them using
+  // `UpdateMarkingWorklistAfterYoungGenGC()`.
+  ConcurrentMarking::PauseScope pause_js_marking(heap_->concurrent_marking());
+  CppHeap::PauseConcurrentMarkingScope pause_cpp_marking(
+      CppHeap::From(heap_->cpp_heap()));
+  if (!FLAG_concurrent_marking) {
+    DCHECK(heap_->fast_promotion_mode_);
+    DCHECK(heap_->CanPromoteYoungAndExpandOldGeneration(0));
+  }
+
+  SemiSpaceNewSpace* semi_space_new_space =
+      SemiSpaceNewSpace::From(heap_->new_space());
+  // Move pages from new->old generation.
+  PageRange range(semi_space_new_space->first_allocatable_address(),
+                  semi_space_new_space->top());
+  for (auto it = range.begin(); it != range.end();) {
+    Page* p = (*++it)->prev_page();
+    semi_space_new_space->from_space().RemovePage(p);
+    Page::ConvertNewToOld(p);
+    if (heap_->incremental_marking()->IsMarking())
+      heap_->mark_compact_collector()->RecordLiveSlotsOnPage(p);
+  }
+
+  // Reset new space.
+  if (!semi_space_new_space->Rebalance()) {
+    V8::FatalProcessOutOfMemory(heap_->isolate(), "NewSpace::Rebalance", true);
+  }
+  semi_space_new_space->ResetLinearAllocationArea();
+  semi_space_new_space->set_age_mark(semi_space_new_space->top());
+
+  for (auto it = heap_->new_lo_space()->begin();
+       it != heap_->new_lo_space()->end();) {
+    LargePage* page = *it;
+    // Increment has to happen after we save the page, because it is going to
+    // be removed below.
+    it++;
+    heap_->lo_space()->PromoteNewLargeObject(page);
+  }
+
+  // Fix up special trackers.
+  heap_->external_string_table_.PromoteYoung();
+  // GlobalHandles are updated in PostGarbageCollectonProcessing
+
+  size_t promoted = heap_->new_space()->Size() + heap_->new_lo_space()->Size();
+  heap_->IncrementYoungSurvivorsCounter(promoted);
+  heap_->IncrementPromotedObjectsSize(promoted);
+  heap_->IncrementSemiSpaceCopiedObjectSize(0);
+}
+
+}  // namespace internal
+}  // namespace v8

src/heap/promote-young-generation.h

@@ -0,0 +1,30 @@
+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_HEAP_PROMOTE_YOUNG_GENERATION_H_
+#define V8_HEAP_PROMOTE_YOUNG_GENERATION_H_
+
+namespace v8 {
+namespace internal {
+
+class Heap;
+
+/**
+ * `PromoteYoungGenerationGC` is a special GC mode used in fast promotion mode
+ * to quickly promote all objects in new space to old space, thus evacuating all
+ * of new space and leaving it empty.
+ */
+class PromoteYoungGenerationGC {
+ public:
+  explicit PromoteYoungGenerationGC(Heap* heap) : heap_(heap) {}
+  void EvacuateYoungGeneration();
+
+ private:
+  Heap* const heap_;
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_HEAP_PROMOTE_YOUNG_GENERATION_H_