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

content/common/discardable_shared_memory_heap.cc

 // Copyright 2014 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 "content/common/discardable_shared_memory_heap.h"
 
 #include <algorithm>
 
 #include "base/format_macros.h"
 #include "base/memory/discardable_shared_memory.h"
@@ skipping 378 matching lines @@
 
   base::trace_event::MemoryAllocatorDump* obj_dump =
       pmd->CreateAllocatorDump(segment_dump_name + "/allocated_objects");
   obj_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameObjectCount,
                       base::trace_event::MemoryAllocatorDump::kUnitsObjects,
                       static_cast<uint64_t>(allocated_objects_count));
   obj_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                       base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                       static_cast<uint64_t>(allocated_objects_size_in_bytes));
 
+  // Total size of discardable memory segments locked by the clients.
+  const size_t locked_size = shared_memory->LockedSize();
+  obj_dump->AddScalar("client_locked_size",

[reveman, 2015/09/29 12:29:10]

I think it will be enough to dump the exact locked size. What's actually locked
depends on the OS and the browser process should be responsible for dumping
that.

[ssid, 2015/09/29 16:03:55]

Sounds good.

+                      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                      locked_size);
+
+  // Size of the discardable segment actually locked by the platform
+  // independent lock.
+  obj_dump->AddScalar("actual_locked_size",
+                      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                      locked_size ? size : 0u);
+
   // Emit an ownership edge towards a global allocator dump node. This allows
   // to avoid double-counting segments when both browser and child process emit
   // them. In the special case of single-process-mode, this will be the only
   // dumper active and the single ownership edge will become a no-op in the UI.
   const uint64 tracing_process_id =
       base::trace_event::MemoryDumpManager::GetInstance()
           ->GetTracingProcessId();
   base::trace_event::MemoryAllocatorDumpGuid shared_segment_guid =
       GetSegmentGUIDForTracing(tracing_process_id, segment_id);
   pmd->CreateSharedGlobalAllocatorDump(shared_segment_guid);
@@ skipping 28 matching lines @@
   ScopedVector<ScopedMemorySegment>::const_iterator it =
       std::find_if(memory_segments_.begin(), memory_segments_.end(),
                    [span](const ScopedMemorySegment* segment) {
                      return segment->ContainsSpan(span);
                    });
   DCHECK(it != memory_segments_.end());
   return (*it)->CreateMemoryAllocatorDump(span, block_size_, name, pmd);
 }
 
 }  // namespace content