[vm] Delay allocating the ObjectIdRing until the first service request or response.

Avoids GC overhead when the VM service is not in use.

Change-Id: Ic2e752c17fdd01045e30dd62e16f20896a9fc64e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/146440
Reviewed-by: Alexander Aprelev <aam@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/vm/heap/become.cc

@@ -296,8 +296,9 @@ void Become::FollowForwardingPointers(Thread* thread) {
   isolate_group->ForEachIsolate(
       [&](Isolate* isolate) {
         ObjectIdRing* ring = isolate->object_id_ring();
-        ASSERT(ring != NULL);
-        ring->VisitPointers(&pointer_visitor);
+        if (ring != nullptr) {
+          ring->VisitPointers(&pointer_visitor);
+        }
       },
       /*at_safepoint=*/true);
 #endif  // !PRODUCT

runtime/vm/heap/compactor.cc

@@ -418,7 +418,10 @@ void CompactorTask::RunEnteredIsolateGroup() {
           TIMELINE_FUNCTION_GC_DURATION(thread, "ForwardObjectIdRing");
           isolate_group_->ForEachIsolate(
               [&](Isolate* isolate) {
-                isolate->object_id_ring()->VisitPointers(compactor_);
+                ObjectIdRing* ring = isolate->object_id_ring();
+                if (ring != nullptr) {
+                  ring->VisitPointers(compactor_);
+                }
               },
               /*at_safepoint=*/true);
           break;

runtime/vm/isolate.cc

@@ -1475,9 +1475,6 @@ Isolate::Isolate(IsolateGroup* isolate_group,
 #undef ISOLATE_METRIC_CONSTRUCTORS
           reload_every_n_stack_overflow_checks_(FLAG_reload_every),
 #endif  // !defined(PRODUCT)
-#if !defined(PRODUCT)
-      object_id_ring_(new ObjectIdRing()),
-#endif
       start_time_micros_(OS::GetCurrentMonotonicMicros()),
       random_(),
       mutex_(NOT_IN_PRODUCT("Isolate::mutex_")),
@@ -2780,7 +2777,10 @@ void IsolateGroup::VisitStackPointers(ObjectPointerVisitor* visitor,
 void IsolateGroup::VisitObjectIdRingPointers(ObjectPointerVisitor* visitor) {
 #if !defined(PRODUCT)
   for (Isolate* isolate : isolates_) {
-    isolate->object_id_ring()->VisitPointers(visitor);
+    ObjectIdRing* ring = isolate->object_id_ring();
+    if (ring != nullptr) {
+      ring->VisitPointers(visitor);
+    }
   }
 #endif  // !defined(PRODUCT)
 }
@@ -2840,6 +2840,15 @@ intptr_t IsolateGroup::GetClassSizeForHeapWalkAt(intptr_t cid) {
 #endif  // !defined(PRODUCT) && !defined(DART_PRECOMPILED_RUNTIME)
 }
 
+#if !defined(PRODUCT)
+ObjectIdRing* Isolate::EnsureObjectIdRing() {
+  if (object_id_ring_ == nullptr) {
+    object_id_ring_ = new ObjectIdRing();
+  }
+  return object_id_ring_;
+}
+#endif  // !defined(PRODUCT)
+
 void Isolate::AddPendingDeopt(uword fp, uword pc) {
   // GrowableArray::Add is not atomic and may be interrupt by a profiler
   // stack walk.

runtime/vm/isolate.h

@@ -955,7 +955,8 @@ class Isolate : public BaseIsolate, public IntrusiveDListEntry<Isolate> {
   }
 
 #if !defined(PRODUCT)
-  ObjectIdRing* object_id_ring() { return object_id_ring_; }
+  ObjectIdRing* object_id_ring() const { return object_id_ring_; }
+  ObjectIdRing* EnsureObjectIdRing();
 #endif  // !defined(PRODUCT)
 
   void AddPendingDeopt(uword fp, uword pc);

runtime/vm/json_stream.cc

@@ -41,7 +41,7 @@ JSONStream::JSONStream(intptr_t buf_size)
   ObjectIdRing* ring = NULL;
   Isolate* isolate = Isolate::Current();
   if (isolate != NULL) {
-    ring = isolate->object_id_ring();
+    ring = isolate->EnsureObjectIdRing();
   }
   default_id_zone_.Init(ring, ObjectIdRing::kAllocateId);
 }

runtime/vm/object_id_ring.cc

@@ -86,16 +86,16 @@ void ObjectIdRing::PrintJSON(JSONStream* js) {
   }
 }
 
-ObjectIdRing::ObjectIdRing(int32_t capacity) {
-  ASSERT(capacity > 0);
+ObjectIdRing::ObjectIdRing() {
   serial_num_ = 0;
   wrapped_ = false;
   table_ = NULL;
-  SetCapacityAndMaxSerial(capacity, kMaxId);
+  SetCapacityAndMaxSerial(kDefaultCapacity, kMaxId);
 }
 
 void ObjectIdRing::SetCapacityAndMaxSerial(int32_t capacity,
                                            int32_t max_serial) {
+  ASSERT(capacity > 0);
   ASSERT(max_serial <= kMaxId);
   capacity_ = capacity;
   if (table_ != NULL) {

runtime/vm/object_id_ring.h

@@ -39,7 +39,7 @@ class ObjectIdRing {
   static const int32_t kInvalidId = -1;
   static const int32_t kDefaultCapacity = 8192;
 
-  explicit ObjectIdRing(int32_t capacity = kDefaultCapacity);
+  ObjectIdRing();
   ~ObjectIdRing();
 
   // Adds the argument to the ring and returns its id. Note we do not allow

runtime/vm/object_id_ring_test.cc

@@ -52,7 +52,7 @@ class ObjectIdRingTestHelper {
 // Test that serial number wrapping works.
 ISOLATE_UNIT_TEST_CASE(ObjectIdRingSerialWrapTest) {
   Isolate* isolate = Isolate::Current();
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
   ObjectIdRingTestHelper::SetCapacityAndMaxSerial(ring, 2, 4);
   intptr_t id;
   ObjectIdRing::LookupResult kind = ObjectIdRing::kInvalid;
@@ -137,7 +137,7 @@ TEST_CASE(ObjectIdRingScavengeMoveTest) {
   EXPECT_EQ(3, list_length);
 
   Isolate* isolate = thread->isolate();
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
   ObjectIdRing::LookupResult kind = ObjectIdRing::kInvalid;
 
   {
@@ -196,7 +196,7 @@ TEST_CASE(ObjectIdRingScavengeMoveTest) {
 // Test that the ring table is updated with nulls when the old GC collects.
 ISOLATE_UNIT_TEST_CASE(ObjectIdRingOldGCTest) {
   Isolate* isolate = thread->isolate();
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
 
   ObjectIdRing::LookupResult kind = ObjectIdRing::kInvalid;
   intptr_t raw_obj_id1 = -1;
@@ -241,7 +241,7 @@ ISOLATE_UNIT_TEST_CASE(ObjectIdRingOldGCTest) {
 // overridden by new entries.
 ISOLATE_UNIT_TEST_CASE(ObjectIdRingExpiredEntryTest) {
   Isolate* isolate = Isolate::Current();
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
 
   // Insert an object and check we can look it up.
   String& obj = String::Handle(String::New("I will expire"));

runtime/vm/service.cc

@@ -1685,8 +1685,7 @@ static ObjectPtr LookupObjectId(Thread* thread,
     return Object::null();
   }
 
-  ObjectIdRing* ring = thread->isolate()->object_id_ring();
-  ASSERT(ring != NULL);
+  ObjectIdRing* ring = thread->isolate()->EnsureObjectIdRing();
   intptr_t id = -1;
   if (!GetIntegerId(arg, &id)) {
     *kind = ObjectIdRing::kInvalid;

runtime/vm/service_test.cc

@@ -186,7 +186,7 @@ ISOLATE_UNIT_TEST_CASE(Service_IsolateStickyError) {
 ISOLATE_UNIT_TEST_CASE(Service_IdZones) {
   Zone* zone = thread->zone();
   Isolate* isolate = thread->isolate();
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
 
   const String& test_a = String::Handle(zone, String::New("a"));
   const String& test_b = String::Handle(zone, String::New("b"));
@@ -384,7 +384,7 @@ ISOLATE_UNIT_TEST_CASE(Service_PcDescriptors) {
   const PcDescriptors& descriptors =
       PcDescriptors::Handle(code_c.pc_descriptors());
   EXPECT(!descriptors.IsNull());
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
   intptr_t id = ring->GetIdForObject(descriptors.raw());
 
   // Build a mock message handler and wrap it in a dart port.
@@ -455,7 +455,7 @@ ISOLATE_UNIT_TEST_CASE(Service_LocalVarDescriptors) {
   const LocalVarDescriptors& descriptors =
       LocalVarDescriptors::Handle(code_c.GetLocalVarDescriptors());
   // Generate an ID for this object.
-  ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing* ring = isolate->EnsureObjectIdRing();
   intptr_t id = ring->GetIdForObject(descriptors.raw());
 
   // Build a mock message handler and wrap it in a dart port.