[heap] Introduce AllocationCounter class to manage allocation observers

AllocationCounter just stores all allocation observers for now.

Bug: v8:10315
Change-Id: I4ff4208877dd9454c9eef5e5d2e2349b7f00065f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2306793
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68942}

src/heap/allocation-observer.cc

@@ -10,6 +10,17 @@
 namespace v8 {
 namespace internal {
 
+void AllocationCounter::AddAllocationObserver(AllocationObserver* observer) {
+  allocation_observers_.push_back(observer);
+}
+
+void AllocationCounter::RemoveAllocationObserver(AllocationObserver* observer) {
+  auto it = std::find(allocation_observers_.begin(),
+                      allocation_observers_.end(), observer);
+  DCHECK(allocation_observers_.end() != it);
+  allocation_observers_.erase(it);
+}
+
 void AllocationObserver::AllocationStep(int bytes_allocated,
                                         Address soon_object, size_t size) {
   DCHECK_GE(bytes_allocated, 0);

src/heap/allocation-observer.h

@@ -5,11 +5,30 @@
 #ifndef V8_HEAP_ALLOCATION_OBSERVER_H_
 #define V8_HEAP_ALLOCATION_OBSERVER_H_
 
+#include <vector>
+
 #include "src/common/globals.h"
 
 namespace v8 {
 namespace internal {
 
+class AllocationObserver;
+
+class AllocationCounter {
+ public:
+  auto begin() { return allocation_observers_.begin(); }
+  auto end() { return allocation_observers_.end(); }
+
+  void AddAllocationObserver(AllocationObserver* observer);
+  void RemoveAllocationObserver(AllocationObserver* observer);
+
+  bool HasAllocationObservers() { return !allocation_observers_.empty(); }
+  size_t NumberAllocationObservers() { return allocation_observers_.size(); }
+
+ private:
+  std::vector<AllocationObserver*> allocation_observers_;
+};
+
 // -----------------------------------------------------------------------------
 // Allows observation of allocations.
 class AllocationObserver {

src/heap/spaces.cc

@@ -248,15 +248,12 @@ void Page::DestroyBlackAreaBackground(Address start, Address end) {
 // PagedSpace implementation
 
 void Space::AddAllocationObserver(AllocationObserver* observer) {
-  allocation_observers_.push_back(observer);
+  allocation_counter_.AddAllocationObserver(observer);
   StartNextInlineAllocationStep();
 }
 
 void Space::RemoveAllocationObserver(AllocationObserver* observer) {
-  auto it = std::find(allocation_observers_.begin(),
-                      allocation_observers_.end(), observer);
-  DCHECK(allocation_observers_.end() != it);
-  allocation_observers_.erase(it);
+  allocation_counter_.RemoveAllocationObserver(observer);
   StartNextInlineAllocationStep();
 }
 
@@ -275,7 +272,7 @@ void Space::AllocationStep(int bytes_since_last, Address soon_object,
   DCHECK(!heap()->allocation_step_in_progress());
   heap()->set_allocation_step_in_progress(true);
   heap()->CreateFillerObjectAt(soon_object, size, ClearRecordedSlots::kNo);
-  for (AllocationObserver* observer : allocation_observers_) {
+  for (AllocationObserver* observer : allocation_counter_) {
     observer->AllocationStep(bytes_since_last, soon_object, size);
   }
   heap()->set_allocation_step_in_progress(false);
@@ -288,7 +285,7 @@ void Space::AllocationStepAfterMerge(Address first_object_in_chunk, int size) {
 
   DCHECK(!heap()->allocation_step_in_progress());
   heap()->set_allocation_step_in_progress(true);
-  for (AllocationObserver* observer : allocation_observers_) {
+  for (AllocationObserver* observer : allocation_counter_) {
     observer->AllocationStep(size, first_object_in_chunk, size);
   }
   heap()->set_allocation_step_in_progress(false);
@@ -296,11 +293,11 @@ void Space::AllocationStepAfterMerge(Address first_object_in_chunk, int size) {
 
 intptr_t Space::GetNextInlineAllocationStepSize() {
   intptr_t next_step = 0;
-  for (AllocationObserver* observer : allocation_observers_) {
+  for (AllocationObserver* observer : allocation_counter_) {
     next_step = next_step ? Min(next_step, observer->bytes_to_next_step())
                           : observer->bytes_to_next_step();
   }
-  DCHECK(allocation_observers_.size() == 0 || next_step > 0);
+  DCHECK(!allocation_counter_.HasAllocationObservers() || next_step > 0);
   return next_step;
 }
 
@@ -405,7 +402,8 @@ void SpaceWithLinearArea::AddAllocationObserver(AllocationObserver* observer) {
 void SpaceWithLinearArea::RemoveAllocationObserver(
     AllocationObserver* observer) {
   Address top_for_next_step =
-      allocation_observers_.size() == 1 ? kNullAddress : top();
+      allocation_counter_.NumberAllocationObservers() == 1 ? kNullAddress
+                                                           : top();
   InlineAllocationStep(top(), top_for_next_step, kNullAddress, 0);
   Space::RemoveAllocationObserver(observer);
   DCHECK_IMPLIES(top_on_previous_step_, AllocationObserversActive());

src/heap/spaces.h

@@ -12,6 +12,7 @@
 #include "src/base/iterator.h"
 #include "src/base/macros.h"
 #include "src/common/globals.h"
+#include "src/heap/allocation-observer.h"
 #include "src/heap/base-space.h"
 #include "src/heap/basic-memory-chunk.h"
 #include "src/heap/free-list.h"
@@ -193,10 +194,11 @@ class V8_EXPORT_PRIVATE Space : public BaseSpace {
  protected:
   intptr_t GetNextInlineAllocationStepSize();
   bool AllocationObserversActive() {
-    return !allocation_observers_paused_ && !allocation_observers_.empty();
+    return !allocation_observers_paused_ &&
+           allocation_counter_.HasAllocationObservers();
   }
 
-  std::vector<AllocationObserver*> allocation_observers_;
+  AllocationCounter allocation_counter_;
 
   // The List manages the pages that belong to the given space.
   heap::List<MemoryChunk> memory_chunk_list_;