Sampling heap profiler: Force Full GC before retrieving the profile.

BUG=v8:4959
LOG=N

Review-Url: https://codereview.chromium.org/1949693003
Cr-Commit-Position: refs/heads/master@{#36042}

include/v8-profiler.h

@@ -515,6 +515,11 @@ class V8_EXPORT AllocationProfile {
  */
 class V8_EXPORT HeapProfiler {
  public:
+  enum SamplingFlags {
+    kSamplingNoFlags = 0,
+    kSamplingForceGC = 1 << 0,
+  };
+
   /**
    * Callback function invoked for obtaining RetainedObjectInfo for
    * the given JavaScript wrapper object. It is prohibited to enter V8
@@ -640,7 +645,8 @@ class V8_EXPORT HeapProfiler {
    * Returns false if a sampling heap profiler is already running.
    */
   bool StartSamplingHeapProfiler(uint64_t sample_interval = 512 * 1024,
-                                 int stack_depth = 16);
+                                 int stack_depth = 16,
+                                 SamplingFlags flags = kSamplingNoFlags);
 
   /**
    * Stops the sampling heap profile and discards the current profile.

src/api.cc

@@ -8528,11 +8528,11 @@ SnapshotObjectId HeapProfiler::GetHeapStats(OutputStream* stream,
   return heap_profiler->PushHeapObjectsStats(stream, timestamp_us);
 }
 
-
 bool HeapProfiler::StartSamplingHeapProfiler(uint64_t sample_interval,
-                                             int stack_depth) {
-  return reinterpret_cast<i::HeapProfiler*>(this)
-      ->StartSamplingHeapProfiler(sample_interval, stack_depth);
+                                             int stack_depth,
+                                             SamplingFlags flags) {
+  return reinterpret_cast<i::HeapProfiler*>(this)->StartSamplingHeapProfiler(
+      sample_interval, stack_depth, flags);
 }
 
 

src/profiler/heap-profiler.cc

@@ -84,14 +84,14 @@ HeapSnapshot* HeapProfiler::TakeSnapshot(
   return result;
 }
 
-
-bool HeapProfiler::StartSamplingHeapProfiler(uint64_t sample_interval,
-                                             int stack_depth) {
+bool HeapProfiler::StartSamplingHeapProfiler(
+    uint64_t sample_interval, int stack_depth,
+    v8::HeapProfiler::SamplingFlags flags) {
   if (sampling_heap_profiler_.get()) {
     return false;
   }
   sampling_heap_profiler_.Reset(new SamplingHeapProfiler(
-      heap(), names_.get(), sample_interval, stack_depth));
+      heap(), names_.get(), sample_interval, stack_depth, flags));
   return true;
 }
 

src/profiler/heap-profiler.h

@@ -30,7 +30,8 @@ class HeapProfiler {
       v8::ActivityControl* control,
       v8::HeapProfiler::ObjectNameResolver* resolver);
 
-  bool StartSamplingHeapProfiler(uint64_t sample_interval, int stack_depth);
+  bool StartSamplingHeapProfiler(uint64_t sample_interval, int stack_depth,
+                                 v8::HeapProfiler::SamplingFlags);
   void StopSamplingHeapProfiler();
   bool is_sampling_allocations() { return !sampling_heap_profiler_.is_empty(); }
   AllocationProfile* GetAllocationProfile();

src/profiler/sampling-heap-profiler.cc

@@ -47,8 +47,9 @@ v8::AllocationProfile::Allocation SamplingHeapProfiler::ScaleSample(
   return {size, static_cast<unsigned int>(count * scale + 0.5)};
 }
 
-SamplingHeapProfiler::SamplingHeapProfiler(Heap* heap, StringsStorage* names,
-                                           uint64_t rate, int stack_depth)
+SamplingHeapProfiler::SamplingHeapProfiler(
+    Heap* heap, StringsStorage* names, uint64_t rate, int stack_depth,
+    v8::HeapProfiler::SamplingFlags flags)
     : isolate_(heap->isolate()),
       heap_(heap),
       new_space_observer_(new SamplingAllocationObserver(
@@ -61,7 +62,8 @@ SamplingHeapProfiler::SamplingHeapProfiler(Heap* heap, StringsStorage* names,
       profile_root_(nullptr, "(root)", v8::UnboundScript::kNoScriptId, 0),
       samples_(),
       stack_depth_(stack_depth),
-      rate_(rate) {
+      rate_(rate),
+      flags_(flags) {
   CHECK_GT(rate_, 0);
   heap->new_space()->AddAllocationObserver(new_space_observer_.get());
   AllSpaces spaces(heap);
@@ -257,6 +259,10 @@ v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
 }
 
 v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
+  if (flags_ & v8::HeapProfiler::kSamplingForceGC) {
+    isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags,
+                                        "SamplingHeapProfiler");
+  }
   // To resolve positions to line/column numbers, we will need to look up
   // scripts. Build a map to allow fast mapping from script id to script.
   std::map<int, Handle<Script>> scripts;

src/profiler/sampling-heap-profiler.h

@@ -41,7 +41,7 @@ class AllocationProfile : public v8::AllocationProfile {
 class SamplingHeapProfiler {
  public:
   SamplingHeapProfiler(Heap* heap, StringsStorage* names, uint64_t rate,
-                       int stack_depth);
+                       int stack_depth, v8::HeapProfiler::SamplingFlags flags);
   ~SamplingHeapProfiler();
 
   v8::AllocationProfile* GetAllocationProfile();
@@ -130,6 +130,7 @@ class SamplingHeapProfiler {
   std::set<Sample*> samples_;
   const int stack_depth_;
   const uint64_t rate_;
+  v8::HeapProfiler::SamplingFlags flags_;
 
   friend class SamplingAllocationObserver;
 };