[heap] Perform GC in a shared heap

This CL implements GC in a shared heap. A shared GC is started from
an attached client isolate that fails to allocate a shared object. In
order to perform a shared GC all other running client isolates need
to be stopped and their roots need to be scanned.

Bug: v8:11708
Change-Id: I45ac50e6b4a1e9270f9e39b69f9b8ee5e6e14134
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2964816Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75606}

src/common/globals.h

@@ -841,6 +841,11 @@ inline std::ostream& operator<<(std::ostream& os, AllocationType kind) {
   UNREACHABLE();
 }
 
+inline constexpr bool IsSharedAllocationType(AllocationType kind) {
+  return kind == AllocationType::kSharedOld ||
+         kind == AllocationType::kSharedMap;
+}
+
 // TODO(ishell): review and rename kWordAligned to kTaggedAligned.
 enum AllocationAlignment { kWordAligned, kDoubleAligned, kDoubleUnaligned };
 

src/execution/isolate.h

@@ -1802,6 +1802,16 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
   bool HasClientIsolates() const { return client_isolate_head_; }
 
+  template <typename Callback>
+  void IterateClientIsolates(Callback callback) {
+    for (Isolate* current = client_isolate_head_; current;
+         current = current->next_client_isolate_) {
+      callback(current);
+    }
+  }
+
+  base::Mutex* client_isolate_mutex() { return &client_isolate_mutex_; }
+
  private:
   explicit Isolate(std::unique_ptr<IsolateAllocator> isolate_allocator,
                    bool is_shared);

src/heap/heap.cc

@@ -2172,9 +2172,6 @@ size_t Heap::PerformGarbageCollection(
 
   SafepointScope safepoint_scope(this);
 
-  // Shared isolates cannot have any clients when running GC at the moment.
-  DCHECK_IMPLIES(IsShared(), !isolate()->HasClientIsolates());
-
   collection_barrier_->StopTimeToCollectionTimer();
 
 #ifdef VERIFY_HEAP
@@ -2262,6 +2259,50 @@ size_t Heap::PerformGarbageCollection(
   return freed_global_handles;
 }
 
+void Heap::CollectSharedGarbage(GarbageCollectionReason gc_reason) {
+  DCHECK(!IsShared());
+  DCHECK_NOT_NULL(isolate()->shared_isolate());
+
+  isolate()->shared_isolate()->heap()->PerformSharedGarbageCollection(
+      isolate(), gc_reason);
+}
+
+void Heap::PerformSharedGarbageCollection(Isolate* initiator,
+                                          GarbageCollectionReason gc_reason) {
+  DCHECK(IsShared());
+  base::MutexGuard guard(isolate()->client_isolate_mutex());
+
+  const char* collector_reason = nullptr;
+  GarbageCollector collector = MARK_COMPACTOR;
+
+  tracer()->Start(collector, gc_reason, collector_reason);
+
+  isolate()->IterateClientIsolates([initiator](Isolate* client) {
+    DCHECK_NOT_NULL(client->shared_isolate());
+    Heap* client_heap = client->heap();
+
+    GlobalSafepoint::StopMainThread stop_main_thread =
+        initiator == client ? GlobalSafepoint::StopMainThread::kNo
+                            : GlobalSafepoint::StopMainThread::kYes;
+
+    client_heap->safepoint()->EnterSafepointScope(stop_main_thread);
+
+    client_heap->shared_old_allocator_->FreeLinearAllocationArea();
+    client_heap->shared_map_allocator_->FreeLinearAllocationArea();
+  });
+
+  PerformGarbageCollection(MARK_COMPACTOR);
+
+  isolate()->IterateClientIsolates([initiator](Isolate* client) {
+    GlobalSafepoint::StopMainThread stop_main_thread =
+        initiator == client ? GlobalSafepoint::StopMainThread::kNo
+                            : GlobalSafepoint::StopMainThread::kYes;
+    client->heap()->safepoint()->LeaveSafepointScope(stop_main_thread);
+  });
+
+  tracer()->Stop(collector);
+}
+
 void Heap::CompleteSweepingYoung(GarbageCollector collector) {
   GCTracer::Scope::ScopeId scope_id;
 
@@ -4322,10 +4363,7 @@ void Heap::Verify() {
   SafepointScope safepoint_scope(this);
   HandleScope scope(isolate());
 
-  MakeLocalHeapLabsIterable();
-
-  // We have to wait here for the sweeper threads to have an iterable heap.
-  mark_compact_collector()->EnsureSweepingCompleted();
+  MakeHeapIterable();
 
   array_buffer_sweeper()->EnsureFinished();
 
@@ -4792,6 +4830,15 @@ void Heap::IterateRoots(RootVisitor* v, base::EnumSet<SkipRoot> options) {
   }
 }
 
+void Heap::IterateRootsIncludingClients(RootVisitor* v,
+                                        base::EnumSet<SkipRoot> options) {
+  IterateRoots(v, options);
+
+  isolate()->IterateClientIsolates([v, options](Isolate* client) {
+    client->heap()->IterateRoots(v, options);
+  });
+}
+
 void Heap::IterateWeakGlobalHandles(RootVisitor* v) {
   isolate_->global_handles()->IterateWeakRoots(v);
 }
@@ -5340,8 +5387,12 @@ HeapObject Heap::AllocateRawWithLightRetrySlowPath(
   }
   // Two GCs before panicking. In newspace will almost always succeed.
   for (int i = 0; i < 2; i++) {
+    if (IsSharedAllocationType(allocation)) {
+      CollectSharedGarbage(GarbageCollectionReason::kAllocationFailure);
+    } else {
       CollectGarbage(alloc.RetrySpace(),
                      GarbageCollectionReason::kAllocationFailure);
+    }
     alloc = AllocateRaw(size, allocation, origin, alignment);
     if (alloc.To(&result)) {
       DCHECK(result != ReadOnlyRoots(this).exception());
@@ -5360,7 +5411,12 @@ HeapObject Heap::AllocateRawWithRetryOrFailSlowPath(
   if (!result.is_null()) return result;
 
   isolate()->counters()->gc_last_resort_from_handles()->Increment();
+  if (IsSharedAllocationType(allocation)) {
+    CollectSharedGarbage(GarbageCollectionReason::kLastResort);
+  } else {
     CollectAllAvailableGarbage(GarbageCollectionReason::kLastResort);
+  }
+
   {
     AlwaysAllocateScope scope(this);
     alloc = AllocateRaw(size, allocation, origin, alignment);

src/heap/heap.h

@@ -1026,6 +1026,10 @@ class Heap {
       int flags, GarbageCollectionReason gc_reason,
       const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
 
+  // Performs garbage collection operation for the shared heap.
+  V8_EXPORT_PRIVATE void CollectSharedGarbage(
+      GarbageCollectionReason gc_reason);
+
   // Reports and external memory pressure event, either performs a major GC or
   // completes incremental marking in order to free external resources.
   void ReportExternalMemoryPressure();
@@ -1060,6 +1064,9 @@ class Heap {
 
   // Iterates over the strong roots and the weak roots.
   void IterateRoots(RootVisitor* v, base::EnumSet<SkipRoot> options);
+  void IterateRootsIncludingClients(RootVisitor* v,
+                                    base::EnumSet<SkipRoot> options);
+
   // Iterates over entries in the smi roots list.  Only interesting to the
   // serializer/deserializer, since GC does not care about smis.
   void IterateSmiRoots(RootVisitor* v);
@@ -1799,6 +1806,10 @@ class Heap {
       GarbageCollector collector,
       const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
 
+  // Performs garbage collection in the shared heap.
+  void PerformSharedGarbageCollection(Isolate* initiator,
+                                      GarbageCollectionReason gc_reason);
+
   inline void UpdateOldSpaceLimits();
 
   bool CreateInitialMaps();

src/heap/mark-compact.cc

@@ -121,7 +121,8 @@ class MarkingVerifier : public ObjectVisitor, public RootVisitor {
 };
 
 void MarkingVerifier::VerifyRoots() {
-  heap_->IterateRoots(this, base::EnumSet<SkipRoot>{SkipRoot::kWeak});
+  heap_->IterateRootsIncludingClients(this,
+                                      base::EnumSet<SkipRoot>{SkipRoot::kWeak});
 }
 
 void MarkingVerifier::VerifyMarkingOnPage(const Page* page, Address start,
@@ -245,9 +246,10 @@ class FullMarkingVerifier : public MarkingVerifier {
 
  private:
   V8_INLINE void VerifyHeapObjectImpl(HeapObject heap_object) {
-    if (!heap_->IsShared() &&
+    if (heap_->IsShared() !=
         BasicMemoryChunk::FromHeapObject(heap_object)->InSharedHeap())
       return;
+
     CHECK(marking_state_->IsBlackOrGrey(heap_object));
   }
 
@@ -305,7 +307,8 @@ class EvacuationVerifier : public ObjectVisitor, public RootVisitor {
 };
 
 void EvacuationVerifier::VerifyRoots() {
-  heap_->IterateRoots(this, base::EnumSet<SkipRoot>{SkipRoot::kWeak});
+  heap_->IterateRootsIncludingClients(this,
+                                      base::EnumSet<SkipRoot>{SkipRoot::kWeak});
 }
 
 void EvacuationVerifier::VerifyEvacuationOnPage(Address start, Address end) {
@@ -356,6 +359,10 @@ class FullEvacuationVerifier : public EvacuationVerifier {
 
  protected:
   V8_INLINE void VerifyHeapObjectImpl(HeapObject heap_object) {
+    if (heap_->IsShared() !=
+        BasicMemoryChunk::FromHeapObject(heap_object)->InSharedHeap())
+      return;
+
     CHECK_IMPLIES(Heap::InYoungGeneration(heap_object),
                   Heap::InToPage(heap_object));
     CHECK(!MarkCompactCollector::IsOnEvacuationCandidate(heap_object));
@@ -1001,7 +1008,7 @@ class MarkCompactCollector::RootMarkingVisitor final : public RootVisitor {
     HeapObject heap_object = HeapObject::cast(object);
     BasicMemoryChunk* target_page =
         BasicMemoryChunk::FromHeapObject(heap_object);
-    if (!is_shared_heap_ && target_page->InSharedHeap()) return;
+    if (is_shared_heap_ != target_page->InSharedHeap()) return;
     collector_->MarkRootObject(root, heap_object);
   }
 
@@ -1629,10 +1636,16 @@ void MarkCompactCollector::MarkRoots(RootVisitor* root_visitor,
                                      ObjectVisitor* custom_root_body_visitor) {
   // Mark the heap roots including global variables, stack variables,
   // etc., and all objects reachable from them.
-  heap()->IterateRoots(root_visitor, base::EnumSet<SkipRoot>{SkipRoot::kWeak});
+  heap()->IterateRootsIncludingClients(
+      root_visitor, base::EnumSet<SkipRoot>{SkipRoot::kWeak});
 
   // Custom marking for top optimized frame.
-  ProcessTopOptimizedFrame(custom_root_body_visitor);
+  ProcessTopOptimizedFrame(custom_root_body_visitor, isolate());
+
+  isolate()->IterateClientIsolates(
+      [this, custom_root_body_visitor](Isolate* client) {
+        ProcessTopOptimizedFrame(custom_root_body_visitor, client);
+      });
 }
 
 void MarkCompactCollector::VisitObject(HeapObject obj) {
@@ -1921,13 +1934,14 @@ void MarkCompactCollector::ProcessEphemeronMarking() {
   CHECK(heap()->local_embedder_heap_tracer()->IsRemoteTracingDone());
 }
 
-void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
-  for (StackFrameIterator it(isolate(), isolate()->thread_local_top());
-       !it.done(); it.Advance()) {
+void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor,
+                                                    Isolate* isolate) {
+  for (StackFrameIterator it(isolate, isolate->thread_local_top()); !it.done();
+       it.Advance()) {
     if (it.frame()->is_unoptimized()) return;
     if (it.frame()->type() == StackFrame::OPTIMIZED) {
       Code code = it.frame()->LookupCode();
-      if (!code.CanDeoptAt(isolate(), it.frame()->pc())) {
+      if (!code.CanDeoptAt(isolate, it.frame()->pc())) {
         Code::BodyDescriptor::IterateBody(code.map(), code, visitor);
       }
       return;
@@ -3984,8 +3998,9 @@ void MarkCompactCollector::UpdatePointersAfterEvacuation() {
     TRACE_GC(heap()->tracer(),
              GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS_TO_NEW_ROOTS);
     // The external string table is updated at the end.
-    heap_->IterateRoots(&updating_visitor, base::EnumSet<SkipRoot>{
-                                               SkipRoot::kExternalStringTable});
+    heap_->IterateRootsIncludingClients(
+        &updating_visitor,
+        base::EnumSet<SkipRoot>{SkipRoot::kExternalStringTable});
   }
 
   {

src/heap/mark-compact.h

@@ -626,7 +626,7 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
   // If the call-site of the top optimized code was not prepared for
   // deoptimization, then treat embedded pointers in the code as strong as
   // otherwise they can die and try to deoptimize the underlying code.
-  void ProcessTopOptimizedFrame(ObjectVisitor* visitor);
+  void ProcessTopOptimizedFrame(ObjectVisitor* visitor, Isolate* isolate);
 
   // Drains the main thread marking work list. Will mark all pending objects
   // if no concurrent threads are running.

src/heap/safepoint.cc

@@ -21,7 +21,7 @@ namespace internal {
 GlobalSafepoint::GlobalSafepoint(Heap* heap)
     : heap_(heap), local_heaps_head_(nullptr), active_safepoint_scopes_(0) {}
 
-void GlobalSafepoint::EnterSafepointScope() {
+void GlobalSafepoint::EnterSafepointScope(StopMainThread stop_main_thread) {
   if (++active_safepoint_scopes_ > 1) return;
 
   TimedHistogramScope timer(
@@ -37,10 +37,10 @@ void GlobalSafepoint::EnterSafepointScope() {
 
   for (LocalHeap* local_heap = local_heaps_head_; local_heap;
        local_heap = local_heap->next_) {
-    if (local_heap->is_main_thread()) {
+    if (local_heap->is_main_thread() &&
+        stop_main_thread == StopMainThread::kNo) {
       continue;
     }
-    DCHECK(!local_heap->is_main_thread());
 
     LocalHeap::ThreadState expected = local_heap->state_relaxed();
 
@@ -64,7 +64,7 @@ void GlobalSafepoint::EnterSafepointScope() {
   barrier_.WaitUntilRunningThreadsInSafepoint(running);
 }
 
-void GlobalSafepoint::LeaveSafepointScope() {
+void GlobalSafepoint::LeaveSafepointScope(StopMainThread stop_main_thread) {
   DCHECK_GT(active_safepoint_scopes_, 0);
   if (--active_safepoint_scopes_ > 0) return;
 
@@ -72,7 +72,8 @@ void GlobalSafepoint::LeaveSafepointScope() {
 
   for (LocalHeap* local_heap = local_heaps_head_; local_heap;
        local_heap = local_heap->next_) {
-    if (local_heap->is_main_thread()) {
+    if (local_heap->is_main_thread() &&
+        stop_main_thread == StopMainThread::kNo) {
       continue;
     }
 
@@ -151,10 +152,12 @@ void GlobalSafepoint::Barrier::WaitInUnpark() {
 }
 
 SafepointScope::SafepointScope(Heap* heap) : safepoint_(heap->safepoint()) {
-  safepoint_->EnterSafepointScope();
+  safepoint_->EnterSafepointScope(GlobalSafepoint::StopMainThread::kNo);
 }
 
-SafepointScope::~SafepointScope() { safepoint_->LeaveSafepointScope(); }
+SafepointScope::~SafepointScope() {
+  safepoint_->LeaveSafepointScope(GlobalSafepoint::StopMainThread::kNo);
+}
 
 bool GlobalSafepoint::ContainsLocalHeap(LocalHeap* local_heap) {
   base::MutexGuard guard(&local_heaps_mutex_);

src/heap/safepoint.h

@@ -18,8 +18,8 @@ class Heap;
 class LocalHeap;
 class RootVisitor;
 
-// Used to bring all background threads with heap access to a safepoint such
-// that e.g. a garbage collection can be performed.
+// Used to bring all threads with heap access to a safepoint such that e.g. a
+// garbage collection can be performed.
 class GlobalSafepoint {
  public:
   explicit GlobalSafepoint(Heap* heap);
@@ -74,8 +74,10 @@ class GlobalSafepoint {
     void NotifyPark();
   };
 
-  void EnterSafepointScope();
-  void LeaveSafepointScope();
+  enum class StopMainThread { kYes, kNo };
+
+  void EnterSafepointScope(StopMainThread stop_main_thread);
+  void LeaveSafepointScope(StopMainThread stop_main_thread);
 
   template <typename Callback>
   void AddLocalHeap(LocalHeap* local_heap, Callback callback) {
@@ -116,9 +118,10 @@ class GlobalSafepoint {
 
   int active_safepoint_scopes_;
 
-  friend class SafepointScope;
+  friend class Heap;
   friend class LocalHeap;
   friend class PersistentHandles;
+  friend class SafepointScope;
 };
 
 class V8_NODISCARD SafepointScope {

test/cctest/heap/test-shared-heap.cc

@@ -6,6 +6,8 @@
 #include "src/common/globals.h"
 #include "src/handles/handles-inl.h"
 #include "src/heap/heap.h"
+#include "src/objects/fixed-array-inl.h"
+#include "src/objects/fixed-array.h"
 #include "src/objects/heap-object.h"
 #include "test/cctest/cctest.h"
 
@@ -140,7 +142,7 @@ UNINITIALIZED_TEST(ConcurrentAllocationInSharedMapSpace) {
   Isolate::Delete(shared_isolate);
 }
 
-UNINITIALIZED_TEST(SharedCollection) {
+UNINITIALIZED_TEST(SharedCollectionWithoutClients) {
   std::unique_ptr<v8::ArrayBuffer::Allocator> allocator(
       v8::ArrayBuffer::Allocator::NewDefaultAllocator());
 
@@ -155,5 +157,43 @@ UNINITIALIZED_TEST(SharedCollection) {
   Isolate::Delete(shared_isolate);
 }
 
+void AllocateInSharedSpace(Isolate* shared_isolate) {
+  SetupClientIsolateAndRunCallback(
+      shared_isolate,
+      [](v8::Isolate* client_isolate, Isolate* i_client_isolate) {
+        HandleScope scope(i_client_isolate);
+        std::vector<Handle<FixedArray>> arrays;
+        const int kKeptAliveArrays = 1000;
+
+        for (int i = 0; i < kNumIterations * 100; i++) {
+          HandleScope scope(i_client_isolate);
+          Handle<FixedArray> array = i_client_isolate->factory()->NewFixedArray(
+              100, AllocationType::kSharedOld);
+          if (i < kKeptAliveArrays) {
+            // Keep some of those arrays alive across GCs.
+            arrays.push_back(scope.CloseAndEscape(array));
+          }
+        }
+
+        for (Handle<FixedArray> array : arrays) {
+          CHECK_EQ(array->length(), 100);
+        }
+      });
+}
+
+UNINITIALIZED_TEST(SharedCollectionWithOneClient) {
+  FLAG_max_old_space_size = 8;
+  std::unique_ptr<v8::ArrayBuffer::Allocator> allocator(
+      v8::ArrayBuffer::Allocator::NewDefaultAllocator());
+
+  v8::Isolate::CreateParams create_params;
+  create_params.array_buffer_allocator = allocator.get();
+  Isolate* shared_isolate = Isolate::NewShared(create_params);
+
+  AllocateInSharedSpace(shared_isolate);
+
+  Isolate::Delete(shared_isolate);
+}
+
 }  // namespace internal
 }  // namespace v8