[heap] Run cleaning of string table in parallel to other cleaning

Bug: v8:12813
Change-Id: I27bbf5190165a0d919f021bbcf089e203dfed83f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3592955Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80072}

src/heap/gc-tracer.cc

@@ -908,13 +908,14 @@ void GCTracer::PrintNVP() const {
           "heap.external.epilogue=%.1f "
           "heap.external.weak_global_handles=%.1f "
           "clear=%1.f "
+          "clear.external_string_table=%.1f "
           "clear.dependent_code=%.1f "
           "clear.maps=%.1f "
           "clear.slots_buffer=%.1f "
-          "clear.string_table=%.1f "
           "clear.weak_collections=%.1f "
           "clear.weak_lists=%.1f "
           "clear.weak_references=%.1f "
+          "clear.join_job=%.1f "
           "complete.sweep_array_buffers=%.1f "
           "epilogue=%.1f "
           "evacuate=%.1f "
@@ -998,13 +999,14 @@ void GCTracer::PrintNVP() const {
           current_scope(Scope::HEAP_EXTERNAL_EPILOGUE),
           current_scope(Scope::HEAP_EXTERNAL_WEAK_GLOBAL_HANDLES),
           current_scope(Scope::MC_CLEAR),
+          current_scope(Scope::MC_CLEAR_EXTERNAL_STRING_TABLE),
           current_scope(Scope::MC_CLEAR_DEPENDENT_CODE),
           current_scope(Scope::MC_CLEAR_MAPS),
           current_scope(Scope::MC_CLEAR_SLOTS_BUFFER),
-          current_scope(Scope::MC_CLEAR_STRING_TABLE),
           current_scope(Scope::MC_CLEAR_WEAK_COLLECTIONS),
           current_scope(Scope::MC_CLEAR_WEAK_LISTS),
           current_scope(Scope::MC_CLEAR_WEAK_REFERENCES),
+          current_scope(Scope::MC_CLEAR_JOIN_JOB),
           current_scope(Scope::MC_COMPLETE_SWEEP_ARRAY_BUFFERS),
           current_scope(Scope::MC_EPILOGUE), current_scope(Scope::MC_EVACUATE),
           current_scope(Scope::MC_EVACUATE_CANDIDATES),

src/heap/mark-compact.cc

@@ -4,6 +4,7 @@
 
 #include "src/heap/mark-compact.h"
 
+#include <memory>
 #include <unordered_map>
 #include <unordered_set>
 
@@ -1314,10 +1315,9 @@ class MarkCompactCollector::SharedHeapObjectVisitor final
   MarkCompactCollector* const collector_;
 };
 
-class InternalizedStringTableCleaner : public RootVisitor {
+class InternalizedStringTableCleaner final : public RootVisitor {
  public:
-  explicit InternalizedStringTableCleaner(Heap* heap)
-      : heap_(heap), pointers_removed_(0) {}
+  explicit InternalizedStringTableCleaner(Heap* heap) : heap_(heap) {}
 
   void VisitRootPointers(Root root, const char* description,
                          FullObjectSlot start, FullObjectSlot end) override {
@@ -1329,8 +1329,7 @@ class InternalizedStringTableCleaner : public RootVisitor {
                          OffHeapObjectSlot end) override {
     DCHECK_EQ(root, Root::kStringTable);
     // Visit all HeapObject pointers in [start, end).
-    MarkCompactCollector::NonAtomicMarkingState* marking_state =
-        heap_->mark_compact_collector()->non_atomic_marking_state();
+    auto* marking_state = heap_->mark_compact_collector()->marking_state();
     Isolate* isolate = heap_->isolate();
     for (OffHeapObjectSlot p = start; p < end; ++p) {
       Object o = p.load(isolate);
@@ -1346,11 +1345,11 @@ class InternalizedStringTableCleaner : public RootVisitor {
     }
   }
 
-  int PointersRemoved() { return pointers_removed_; }
+  int PointersRemoved() const { return pointers_removed_; }
 
  private:
   Heap* heap_;
-  int pointers_removed_;
+  int pointers_removed_ = 0;
 };
 
 class ExternalStringTableCleaner : public RootVisitor {
@@ -1390,7 +1389,7 @@ class ExternalStringTableCleaner : public RootVisitor {
 class MarkCompactWeakObjectRetainer : public WeakObjectRetainer {
  public:
   explicit MarkCompactWeakObjectRetainer(
-      MarkCompactCollector::NonAtomicMarkingState* marking_state)
+      MarkCompactCollector::MarkingState* marking_state)
       : marking_state_(marking_state) {}
 
   Object RetainAs(Object object) override {
@@ -1420,7 +1419,7 @@ class MarkCompactWeakObjectRetainer : public WeakObjectRetainer {
   }
 
  private:
-  MarkCompactCollector::NonAtomicMarkingState* marking_state_;
+  MarkCompactCollector::MarkingState* const marking_state_;
 };
 
 class RecordMigratedSlotVisitor : public ObjectVisitorWithCageBases {
@@ -2495,31 +2494,94 @@ void MarkCompactCollector::MarkLiveObjects() {
   epoch_++;
 }
 
+namespace {
+
+class ParallelClearingJob final : public v8::JobTask {
+ public:
+  class ClearingItem {
+   public:
+    virtual ~ClearingItem() = default;
+    virtual void Run(JobDelegate* delegate) = 0;
+  };
+
+  ParallelClearingJob() = default;
+  ~ParallelClearingJob() override = default;
+  ParallelClearingJob(const ParallelClearingJob&) = delete;
+  ParallelClearingJob& operator=(const ParallelClearingJob&) = delete;
+
+  // v8::JobTask overrides.
+  void Run(JobDelegate* delegate) override {
+    std::unique_ptr<ClearingItem> item;
+    {
+      base::MutexGuard guard(&items_mutex_);
+      item = std::move(items_.back());
+      items_.pop_back();
+    }
+    item->Run(delegate);
+  }
+
+  size_t GetMaxConcurrency(size_t worker_count) const override {
+    base::MutexGuard guard(&items_mutex_);
+    return items_.size();
+  }
+
+  void Add(std::unique_ptr<ClearingItem> item) {
+    items_.push_back(std::move(item));
+  }
+
+ private:
+  mutable base::Mutex items_mutex_;
+  std::vector<std::unique_ptr<ClearingItem>> items_;
+};
+
+class ClearStringTableJobItem final : public ParallelClearingJob::ClearingItem {
+ public:
+  explicit ClearStringTableJobItem(Isolate* isolate) : isolate_(isolate) {}
+
+  void Run(JobDelegate* delegate) final {
+    if (isolate_->OwnsStringTable()) {
+      TRACE_GC1(isolate_->heap()->tracer(),
+                GCTracer::Scope::MC_CLEAR_STRING_TABLE,
+                delegate->IsJoiningThread() ? ThreadKind::kMain
+                                            : ThreadKind::kBackground);
+      // Prune the string table removing all strings only pointed to by the
+      // string table.  Cannot use string_table() here because the string
+      // table is marked.
+      StringTable* string_table = isolate_->string_table();
+      InternalizedStringTableCleaner internalized_visitor(isolate_->heap());
+      string_table->DropOldData();
+      string_table->IterateElements(&internalized_visitor);
+      string_table->NotifyElementsRemoved(
+          internalized_visitor.PointersRemoved());
+    }
+  }
+
+ private:
+  Isolate* const isolate_;
+};
+
+}  // namespace
+
 void MarkCompactCollector::ClearNonLiveReferences() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR);
 
-  if (isolate()->OwnsStringTable()) {
-    TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR_STRING_TABLE);
+  auto clearing_job = std::make_unique<ParallelClearingJob>();
+  clearing_job->Add(std::make_unique<ClearStringTableJobItem>(isolate()));
+  auto clearing_job_handle = V8::GetCurrentPlatform()->PostJob(
+      TaskPriority::kUserBlocking, std::move(clearing_job));
 
-    // Prune the string table removing all strings only pointed to by the
-    // string table.  Cannot use string_table() here because the string
-    // table is marked.
-    StringTable* string_table = isolate()->string_table();
-    InternalizedStringTableCleaner internalized_visitor(heap());
-    string_table->DropOldData();
-    string_table->IterateElements(&internalized_visitor);
-    string_table->NotifyElementsRemoved(internalized_visitor.PointersRemoved());
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR_EXTERNAL_STRING_TABLE);
+    ExternalStringTableCleaner external_visitor(heap());
+    heap()->external_string_table_.IterateAll(&external_visitor);
+    heap()->external_string_table_.CleanUpAll();
   }
 
-  ExternalStringTableCleaner external_visitor(heap());
-  heap()->external_string_table_.IterateAll(&external_visitor);
-  heap()->external_string_table_.CleanUpAll();
-
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR_FLUSHABLE_BYTECODE);
-    // ProcessFlusheBaselineCandidates should be called after clearing bytecode
-    // so that we flush any bytecode if needed so we could correctly set the
-    // code object on the JSFunction.
+    // `ProcessFlusheBaselineCandidates()` must be called after
+    // `ProcessOldCodeCandidates()` so that we correctly set the code object on
+    // the JSFunction after flushing.
     ProcessOldCodeCandidates();
     ProcessFlushedBaselineCandidates();
   }
@@ -2532,8 +2594,7 @@ void MarkCompactCollector::ClearNonLiveReferences() {
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR_WEAK_LISTS);
     // Process the weak references.
-    MarkCompactWeakObjectRetainer mark_compact_object_retainer(
-        non_atomic_marking_state());
+    MarkCompactWeakObjectRetainer mark_compact_object_retainer(marking_state());
     heap()->ProcessAllWeakReferences(&mark_compact_object_retainer);
   }
 
@@ -2562,6 +2623,11 @@ void MarkCompactCollector::ClearNonLiveReferences() {
   }
 #endif  // V8_SANDBOXED_EXTERNAL_POINTERS
 
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR_JOIN_JOB);
+    clearing_job_handle->Join();
+  }
+
   DCHECK(weak_objects_.transition_arrays.IsEmpty());
   DCHECK(weak_objects_.weak_references.IsEmpty());
   DCHECK(weak_objects_.weak_objects_in_code.IsEmpty());
@@ -2676,8 +2742,8 @@ void MarkCompactCollector::FlushBytecodeFromSFI(
 
   // Mark the uncompiled data as black, and ensure all fields have already been
   // marked.
-  DCHECK(non_atomic_marking_state()->IsBlackOrGrey(inferred_name));
-  non_atomic_marking_state()->WhiteToBlack(uncompiled_data);
+  DCHECK(marking_state()->IsBlackOrGrey(inferred_name));
+  marking_state()->WhiteToBlack(uncompiled_data);
 
   // Use the raw function data setter to avoid validity checks, since we're
   // performing the unusual task of decompiling.

src/init/heap-symbols.h

@@ -535,8 +535,10 @@
   F(MARK_COMPACTOR)                                  \
   TOP_MC_SCOPES(F)                                   \
   F(MC_CLEAR_DEPENDENT_CODE)                         \
+  F(MC_CLEAR_EXTERNAL_STRING_TABLE)                  \
   F(MC_CLEAR_FLUSHABLE_BYTECODE)                     \
   F(MC_CLEAR_FLUSHED_JS_FUNCTIONS)                   \
+  F(MC_CLEAR_JOIN_JOB)                               \
   F(MC_CLEAR_MAPS)                                   \
   F(MC_CLEAR_SLOTS_BUFFER)                           \
   F(MC_CLEAR_STRING_TABLE)                           \