[tracing] Display the locked size of discardable memory segment.

content/common/discardable_shared_memory_heap.cc

Index: content/common/discardable_shared_memory_heap.cc
diff --git a/content/common/discardable_shared_memory_heap.cc b/content/common/discardable_shared_memory_heap.cc
index ccf2729c557f660e3b675def1393449be60564dd..cec67258e04d9736c633393e0c6eb3a74f35b5e1 100644
--- a/content/common/discardable_shared_memory_heap.cc
+++ b/content/common/discardable_shared_memory_heap.cc
@@ -278,6 +278,7 @@ DiscardableSharedMemoryHeap::Carve(Span* span, size_t blocks) {
   if (extra) {
     scoped_ptr<Span> leftover(
         new Span(serving->shared_memory_, serving->start_ + blocks, extra));
+    leftover->set_is_locked(false);
     DCHECK_IMPLIES(extra > 1, spans_.find(leftover->start_) == spans_.end());
     RegisterSpan(leftover.get());
 
@@ -367,14 +368,17 @@ void DiscardableSharedMemoryHeap::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd) {
   size_t allocated_objects_count = 0;
   size_t allocated_objects_size_in_bytes = 0;
+  size_t locked_size_in_bytes = 0;

[reveman, 2015/10/01 10:34:39]

nit: locked_objects_size_in_bytes to be consistent with above variables.

[ssid, 2015/10/01 14:08:46]

Done.

   size_t offset =
       reinterpret_cast<size_t>(shared_memory->memory()) / block_size_;
   size_t end = offset + size / block_size_;
   while (offset < end) {
     Span* span = spans_[offset];
     if (!IsInFreeList(span)) {
+      const size_t span_size = span->length_ * block_size_;

[reveman, 2015/10/01 10:34:39]

How about computing allocated_objects_size_in_blocks and
locked_objects_size_in_blocks and convert to bytes when you call AddScalar
instead multiplying with block_size_ for each iteration? that also removes the
need for this temporary variable.

[ssid, 2015/10/01 14:08:46]

Done.

+      allocated_objects_size_in_bytes += span_size;
+      locked_size_in_bytes += span->is_locked_ ? span_size : 0;
       allocated_objects_count++;
-      allocated_objects_size_in_bytes += span->length_ * block_size_;
     }
     offset += span->length_;
   }
@@ -395,6 +399,9 @@ void DiscardableSharedMemoryHeap::OnMemoryDump(
   obj_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                       base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                       static_cast<uint64_t>(allocated_objects_size_in_bytes));
+  obj_dump->AddScalar("locked_size",
+                      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                      locked_size_in_bytes);

[reveman, 2015/10/01 10:34:39]

why no static_cast<uint64_t> here but we have one above? either way is fine with
me as long as it's consistent.

[ssid, 2015/10/01 14:08:46]

I think initially it was added since the AddScalar did not accept 64 bit
numbers, that changed now, cleaning up.

 
   // Emit an ownership edge towards a global allocator dump node. This allows
   // to avoid double-counting segments when both browser and child process emit