Collect array buffer allocation sizes for UMA in megabytes.

src/counters.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COUNTERS_H_
 #define V8_COUNTERS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/base/atomic-utils.h"
@@ skipping 210 matching lines @@
 
   const char* name_;
   int min_;
   int max_;
   int num_buckets_;
   void* histogram_;
   bool lookup_done_;
   Isolate* isolate_;
 };
 
+// A histogram base on megabytes. Use method add() to add a value to
+// the table.
+class MegabyteHistogram : public Histogram {
+ public:
+  MegabyteHistogram() {}
+  MegabyteHistogram(const char* name, int min, int max, int num_buckets,
+                    Isolate* isolate)
+      : Histogram(name, min, max, num_buckets, isolate) {}
+
+  void Add(size_t size) {
+    constexpr size_t kBitsInMegabyte = 20;
+    AddSample(static_cast<int>(size >> kBitsInMegabyte));
+  }
+};

[bbudge, 2017/04/03 18:02:41]

This seems like a lot just to scale the sizes, and it might be confusing that
there's an AddSample method on the class. Rather than inherit a new class, why
not create a static conversion method?

 i.e.

int SizeInMegabytes(size_t size) { ...

[kschimpf, 2017/04/03 19:20:55]

After considerable discussion, we decided to move this locally to object.cc for
the moment.

+
 // A HistogramTimer allows distributions of results to be created.
 class HistogramTimer : public Histogram {
  public:
   enum Resolution {
     MILLISECOND,
     MICROSECOND
   };
 
   HistogramTimer() {}
   HistogramTimer(const char* name, int min, int max, Resolution resolution,
@@ skipping 680 matching lines @@
   HR(errors_thrown_per_context, V8.ErrorsThrownPerContext, 0, 200, 20)        \
   HR(debug_feature_usage, V8.DebugFeatureUsage, 1, 7, 7)                      \
   HR(incremental_marking_reason, V8.GCIncrementalMarkingReason, 0, 21, 22)    \
   HR(mark_compact_reason, V8.GCMarkCompactReason, 0, 21, 22)                  \
   HR(scavenge_reason, V8.GCScavengeReason, 0, 21, 22)                         \
   HR(young_generation_handling, V8.GCYoungGenerationHandling, 0, 2, 3)        \
   /* Asm/Wasm. */                                                             \
   HR(wasm_functions_per_asm_module, V8.WasmFunctionsPerModule.asm, 1, 100000, \
      51)                                                                      \
   HR(wasm_functions_per_wasm_module, V8.WasmFunctionsPerModule.wasm, 1,       \
-     100000, 51)                                                              \
-  HR(array_buffer_big_allocations, V8.ArrayBufferBigAllocations, 1, 32, 32)   \
-  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 1, 32, 32)
+     100000, 51)
+
+#define MEGABYTE_HISTOGRAM_RANGE_LIST(HR)                                     \
+  HR(array_buffer_big_allocations, V8.ArrayBufferBigAllocations, 0, 4096, 13) \
+  HR(array_buffer_new_size_failures, V8.ArrayBufferNewSizeFailures, 0, 4096, 13)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                               \
   /* Garbage collection timers. */                                             \
   HT(gc_compactor, V8.GCCompactor, 10000, MILLISECOND)                         \
   HT(gc_finalize, V8.GCFinalizeMC, 10000, MILLISECOND)                         \
   HT(gc_finalize_reduce_memory, V8.GCFinalizeMCReduceMemory, 10000,            \
      MILLISECOND)                                                              \
   HT(gc_scavenger, V8.GCScavenger, 10000, MILLISECOND)                         \
   HT(gc_context, V8.GCContext, 10000,                                          \
      MILLISECOND) /* GC context cleanup time */                                \
@@ skipping 217 matching lines @@
   SC(wasm_lazily_compiled_functions, V8.WasmLazilyCompiledFunctions)
 
 // This file contains all the v8 counters that are in use.
 class Counters {
  public:
 #define HR(name, caption, min, max, num_buckets) \
   Histogram* name() { return &name##_; }
   HISTOGRAM_RANGE_LIST(HR)
 #undef HR
 
+#define HR(name, caption, min, max, num_buckets) \
+  MegabyteHistogram* name() { return &name##_; }
+  MEGABYTE_HISTOGRAM_RANGE_LIST(HR)
+#undef HR
+
 #define HT(name, caption, max, res) \
   HistogramTimer* name() { return &name##_; }
   HISTOGRAM_TIMER_LIST(HT)
 #undef HT
 
 #define AHT(name, caption) \
   AggregatableHistogramTimer* name() { return &name##_; }
   AGGREGATABLE_HISTOGRAM_TIMER_LIST(AHT)
 #undef AHT
 
@@ skipping 89 matching lines @@
 
   void ResetCounters();
   void ResetHistograms();
   RuntimeCallStats* runtime_call_stats() { return &runtime_call_stats_; }
 
  private:
 #define HR(name, caption, min, max, num_buckets) Histogram name##_;
   HISTOGRAM_RANGE_LIST(HR)
 #undef HR
 
+#define HR(name, caption, min, max, num_buckets) MegabyteHistogram name##_;
+  MEGABYTE_HISTOGRAM_RANGE_LIST(HR)
+#undef HR
+
 #define HT(name, caption, max, res) HistogramTimer name##_;
   HISTOGRAM_TIMER_LIST(HT)
 #undef HT
 
 #define AHT(name, caption) \
   AggregatableHistogramTimer name##_;
   AGGREGATABLE_HISTOGRAM_TIMER_LIST(AHT)
 #undef AHT
 
 #define HP(name, caption) \
@@ skipping 48 matching lines @@
 
   explicit Counters(Isolate* isolate);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Counters);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_