[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

components/discardable_memory/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 "components/discardable_memory/common/discardable_shared_memory_heap.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/format_macros.h"
 #include "base/macros.h"
 #include "base/memory/discardable_shared_memory.h"
 #include "base/memory/ptr_util.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/memory_dump_manager.h"
 
 namespace discardable_memory {
 namespace {
 
 bool IsPowerOfTwo(size_t x) {
   return (x & (x - 1)) == 0;
 }
 
@@ skipping 393 matching lines @@
 
   // Emit an ownership edge towards a global allocator dump node. This allows
   // to avoid double-counting segments when both browser and client 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.
   // The global dump is created as a weak dump so that the segment is removed if
   // the browser does not dump it (segment was purged).
   const uint64_t tracing_process_id =
       base::trace_event::MemoryDumpManager::GetInstance()
           ->GetTracingProcessId();
   base::trace_event::MemoryAllocatorDumpGuid shared_segment_guid =

[ssid, 2017/01/24 04:39:50]

We no longer need the logic of global memory dumps in the discardable dump
provider. The connection between the 2 shared memory segments is made by the
sharedmemory's MemoryDumpProvider using global dump guid(s). So, we just need to
add a sub-allocation or ownership edge to the in-process dump. We can remove all
code related to the global dump creations here.

       GetSegmentGUIDForTracing(tracing_process_id, segment_id);
   pmd->CreateWeakSharedGlobalAllocatorDump(shared_segment_guid);
 
   // The size is added to the global dump so that it gets propagated to both the
   // dumps associated.
   pmd->GetSharedGlobalAllocatorDump(shared_segment_guid)
       ->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                   base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                   allocated_objects_size_in_bytes);
 
   // By creating an edge with a higher |importance| (w.r.t. browser-side dumps)
   // the tracing UI will account the effective size of the segment to the
   // client.
   const int kImportance = 2;
   pmd->AddOwnershipEdge(segment_dump->guid(), shared_segment_guid, kImportance);
+  base::SharedMemoryTracker::AddOwnershipEdgeToSharedGlobalDump(
+      pmd, shared_segment_guid,
+      shared_memory->handle(), shared_memory->mapped_size());

[ssid, 2017/01/24 04:39:50]

Okay the right thing to do here is to keep the hierarchy of allocation and add
global dump edges only for the "sharedmemory" dumps and discardable should just
sub-allocate from the "sharedmemory/xx" objects.
So the code should look like:

base::SharedMemoryTracker::AddSuballocation(segment_dump->guid(),
shared_memory->handle(), shared_memory->mapped_size());

Also please do not add edges between 2 global dumps. The UI still does not know
how to deal with this.

 }
 
 // static
 base::trace_event::MemoryAllocatorDumpGuid
 DiscardableSharedMemoryHeap::GetSegmentGUIDForTracing(
     uint64_t tracing_process_id,
     int32_t segment_id) {
   return base::trace_event::MemoryAllocatorDumpGuid(base::StringPrintf(
       "discardable-x-process/%" PRIx64 "/%d", tracing_process_id, segment_id));
 }
@@ skipping 14 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 discardable_memory