[tracing] Track number of allocations in heap profiler

base/trace_event/heap_profiler_heap_dump_writer.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/trace_event/heap_profiler_heap_dump_writer.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <iterator>
@@ skipping 23 matching lines @@
 namespace base {
 namespace trace_event {
 namespace internal {
 namespace {
 
 // Denotes a property of |AllocationContext| to break down by.
 enum class BreakDownMode { kByBacktrace, kByTypeName };
 
 // A group of bytes for which the context shares a prefix.
 struct Bucket {
-  Bucket() : size(0), backtrace_cursor(0), is_broken_down_by_type_name(false) {}
+  Bucket()
+      : size(0),
+        count(0),
+        backtrace_cursor(0),
+        is_broken_down_by_type_name(false) {}
 
-  std::vector<std::pair<const AllocationContext*, size_t>> bytes_by_context;
+  std::vector<std::pair<const AllocationContext*, AllocationMetrics>>
+      metrics_by_context;
 
-  // The sum of the sizes of |bytes_by_context|.
+  // The sum of the sizes of |metrics_by_context|.
   size_t size;
 
+  // The sum of number of allocations of |metrics_by_context|.
+  size_t count;
+
   // The index of the stack frame that has not yet been broken down by. For all
   // elements in this bucket, the stack frames 0 up to (but not including) the
   // cursor, must be equal.
   size_t backtrace_cursor;
 
   // When true, the type name for all elements in this bucket must be equal.
   bool is_broken_down_by_type_name;
 };
 
 // Comparison operator to order buckets by their size.
 bool operator<(const Bucket& lhs, const Bucket& rhs) {
   return lhs.size < rhs.size;
 }
 
 // Groups the allocations in the bucket by |breakBy|. The buckets in the
 // returned list will have |backtrace_cursor| advanced or
 // |is_broken_down_by_type_name| set depending on the property to group by.
 std::vector<Bucket> GetSubbuckets(const Bucket& bucket, BreakDownMode breakBy) {
   base::hash_map<const char*, Bucket> breakdown;
 
   if (breakBy == BreakDownMode::kByBacktrace) {
-    for (const auto& context_and_size : bucket.bytes_by_context) {
-      const Backtrace& backtrace = context_and_size.first->backtrace;
+    for (const auto& context_and_metrics : bucket.metrics_by_context) {
+      const Backtrace& backtrace = context_and_metrics.first->backtrace;
       const char* const* begin = std::begin(backtrace.frames);
       const char* const* end = std::end(backtrace.frames);
       const char* const* cursor = begin + bucket.backtrace_cursor;
 
       // The backtrace in the context is padded with null pointers, but these
       // should not be considered for breakdown. Adjust end to point past the
       // last non-null frame.
       while (begin != end && *(end - 1) == nullptr)
         end--;
 
       DCHECK_LE(cursor, end);
 
       if (cursor != end) {
         Bucket& subbucket = breakdown[*cursor];
-        subbucket.size += context_and_size.second;
-        subbucket.bytes_by_context.push_back(context_and_size);
+        subbucket.size += context_and_metrics.second.size;
+        subbucket.count += context_and_metrics.second.count;
+        subbucket.metrics_by_context.push_back(context_and_metrics);
         subbucket.backtrace_cursor = bucket.backtrace_cursor + 1;
         subbucket.is_broken_down_by_type_name =
             bucket.is_broken_down_by_type_name;
         DCHECK_GT(subbucket.size, 0u);
+        DCHECK_GT(subbucket.count, 0u);
       }
     }
   } else if (breakBy == BreakDownMode::kByTypeName) {
     if (!bucket.is_broken_down_by_type_name) {
-      for (const auto& context_and_size : bucket.bytes_by_context) {
-        const AllocationContext* context = context_and_size.first;
+      for (const auto& context_and_metrics : bucket.metrics_by_context) {
+        const AllocationContext* context = context_and_metrics.first;
         Bucket& subbucket = breakdown[context->type_name];
-        subbucket.size += context_and_size.second;
-        subbucket.bytes_by_context.push_back(context_and_size);
+        subbucket.size += context_and_metrics.second.size;
+        subbucket.count += context_and_metrics.second.count;
+        subbucket.metrics_by_context.push_back(context_and_metrics);
         subbucket.backtrace_cursor = bucket.backtrace_cursor;
         subbucket.is_broken_down_by_type_name = true;
         DCHECK_GT(subbucket.size, 0u);
+        DCHECK_GT(subbucket.count, 0u);
       }
     }
   }
 
   std::vector<Bucket> buckets;
   buckets.reserve(breakdown.size());
   for (auto key_bucket : breakdown)
     buckets.push_back(key_bucket.second);
 
   return buckets;
@@ skipping 56 matching lines @@
                                TypeNameDeduplicator* type_name_deduplicator)
     : stack_frame_deduplicator_(stack_frame_deduplicator),
       type_name_deduplicator_(type_name_deduplicator) {}
 
 HeapDumpWriter::~HeapDumpWriter() {}
 
 bool HeapDumpWriter::AddEntryForBucket(const Bucket& bucket) {
   // The contexts in the bucket are all different, but the [begin, cursor) range
   // is equal for all contexts in the bucket, and the type names are the same if
   // |is_broken_down_by_type_name| is set.
-  DCHECK(!bucket.bytes_by_context.empty());
+  DCHECK(!bucket.metrics_by_context.empty());
 
-  const AllocationContext* context = bucket.bytes_by_context.front().first;
+  const AllocationContext* context = bucket.metrics_by_context.front().first;
 
   const char* const* backtrace_begin = std::begin(context->backtrace.frames);
   const char* const* backtrace_end = backtrace_begin + bucket.backtrace_cursor;
   DCHECK_LE(bucket.backtrace_cursor, arraysize(context->backtrace.frames));
 
   Entry entry;
   entry.stack_frame_id =
       stack_frame_deduplicator_->Insert(backtrace_begin, backtrace_end);
 
   // Deduplicate the type name, or use ID -1 if type name is not set.
   entry.type_id = bucket.is_broken_down_by_type_name
                       ? type_name_deduplicator_->Insert(context->type_name)
                       : -1;
 
   entry.size = bucket.size;
+  entry.count = bucket.count;
 
   auto position_and_inserted = entries_.insert(entry);
   return position_and_inserted.second;
 }
 
 void HeapDumpWriter::BreakDown(const Bucket& bucket) {
   auto by_backtrace = BreakDownBy(bucket, BreakDownMode::kByBacktrace);
   auto by_type_name = BreakDownBy(bucket, BreakDownMode::kByTypeName);
 
   // Insert entries for the buckets. If a bucket was not present before, it has
   // not been broken down before, so recursively continue breaking down in that
   // case. There might be multiple routes to the same entry (first break down
   // by type name, then by backtrace, or first by backtrace and then by type),
   // so a set is used to avoid dumping and breaking down entries more than once.
 
   for (const Bucket& subbucket : by_backtrace)
     if (AddEntryForBucket(subbucket))
       BreakDown(subbucket);
 
   for (const Bucket& subbucket : by_type_name)
     if (AddEntryForBucket(subbucket))
       BreakDown(subbucket);
 }
 
 const std::set<Entry>& HeapDumpWriter::Summarize(
-    const hash_map<AllocationContext, size_t>& bytes_by_context) {
+    const hash_map<AllocationContext, AllocationMetrics>& metrics_by_context) {
   // Start with one bucket that represents the entire heap. Iterate by
   // reference, because the allocation contexts are going to point to allocation
-  // contexts stored in |bytes_by_context|.
+  // contexts stored in |metrics_by_context|.
   Bucket root_bucket;
-  for (const auto& context_and_size : bytes_by_context) {
-    DCHECK_GT(context_and_size.second, 0u);
-    const AllocationContext* context = &context_and_size.first;
-    const size_t size = context_and_size.second;
-    root_bucket.bytes_by_context.push_back(std::make_pair(context, size));
-    root_bucket.size += size;
+  for (const auto& context_and_metrics : metrics_by_context) {
+    DCHECK_GT(context_and_metrics.second.size, 0u);
+    DCHECK_GT(context_and_metrics.second.count, 0u);
+    const AllocationContext* context = &context_and_metrics.first;
+    root_bucket.metrics_by_context.push_back(
+        std::make_pair(context, context_and_metrics.second));
+    root_bucket.size += context_and_metrics.second.size;
+    root_bucket.count += context_and_metrics.second.count;
   }
 
   AddEntryForBucket(root_bucket);
 
   // Recursively break down the heap and fill |entries_| with entries to dump.
   BreakDown(root_bucket);
 
   return entries_;
 }
 
 std::unique_ptr<TracedValue> Serialize(const std::set<Entry>& entries) {
   std::string buffer;
   std::unique_ptr<TracedValue> traced_value(new TracedValue);
 
   traced_value->BeginArray("entries");
 
   for (const Entry& entry : entries) {
     traced_value->BeginDictionary();
 
     // Format size as hexadecimal string into |buffer|.
     SStringPrintf(&buffer, "%" PRIx64, static_cast<uint64_t>(entry.size));
     traced_value->SetString("size", buffer);
 
+    SStringPrintf(&buffer, "%" PRIx64, static_cast<uint64_t>(entry.count));
+    traced_value->SetString("count", buffer);
+
     if (entry.stack_frame_id == -1) {
       // An empty backtrace (which will have ID -1) is represented by the empty
       // string, because there is no leaf frame to reference in |stackFrames|.
       traced_value->SetString("bt", "");
     } else {
       // Format index of the leaf frame as a string, because |stackFrames| is a
       // dictionary, not an array.
       SStringPrintf(&buffer, "%i", entry.stack_frame_id);
       traced_value->SetString("bt", buffer);
     }
 
     // Type ID -1 (cumulative size for all types) is represented by the absence
     // of the "type" key in the dictionary.
     if (entry.type_id != -1) {
       // Format the type ID as a string.
       SStringPrintf(&buffer, "%i", entry.type_id);
       traced_value->SetString("type", buffer);
     }
 
     traced_value->EndDictionary();
   }
 
   traced_value->EndArray();  // "entries"
   return traced_value;
 }
 
 }  // namespace internal
 
 std::unique_ptr<TracedValue> ExportHeapDump(
-    const hash_map<AllocationContext, size_t>& bytes_by_size,
+    const hash_map<AllocationContext, AllocationMetrics>& metrics_by_context,
     StackFrameDeduplicator* stack_frame_deduplicator,
     TypeNameDeduplicator* type_name_deduplicator) {
   internal::HeapDumpWriter writer(stack_frame_deduplicator,
                                   type_name_deduplicator);
-  return Serialize(writer.Summarize(bytes_by_size));
+  return Serialize(writer.Summarize(metrics_by_context));
 }
 
 }  // namespace trace_event
 }  // namespace base