Add support to create memory allocator dump in base::DiscardableMemory

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 958fa82554efecf5d9c4dee25bb6206cf7e891c9..fe3912cad2fc599afe9bfd468a63bad06e584e45 100644
--- a/content/common/discardable_shared_memory_heap.cc
+++ b/content/common/discardable_shared_memory_heap.cc
@@ -60,6 +60,24 @@ bool DiscardableSharedMemoryHeap::ScopedMemorySegment::IsResident() const {
   return heap_->IsMemoryResident(shared_memory_.get());
 }
 
+base::trace_event::MemoryAllocatorDump*
+DiscardableSharedMemoryHeap::ScopedMemorySegment::CreateMemoryAllocatorDump(
+    Span* span,
+    const char* name,
+    base::trace_event::ProcessMemoryDump* pmd) const {
+  if (shared_memory_ != span->shared_memory())
+    return nullptr;
+
+  base::trace_event::MemoryAllocatorDump* dump = pmd->CreateAllocatorDump(name);
+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                  static_cast<uint64_t>(span->length()));
+
+  pmd->AddSuballocation(dump->guid(),
+                        base::StringPrintf("discardable/segment_%d", id_));
+  return dump;
+}
+
 void DiscardableSharedMemoryHeap::ScopedMemorySegment::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd) const {
   heap_->OnMemoryDump(shared_memory_.get(), size_, id_, pmd);
@@ -398,4 +416,27 @@ DiscardableSharedMemoryHeap::GetSegmentGUIDForTracing(uint64 tracing_process_id,
       "discardable-x-process/%" PRIx64 "/%d", tracing_process_id, segment_id));
 }
 
+base::trace_event::MemoryAllocatorDump*
+DiscardableSharedMemoryHeap::CreateMemoryAllocatorDump(
+    Span* span,
+    const char* name,
+    base::trace_event::ProcessMemoryDump* pmd) const {
+  if (span->shared_memory() == nullptr)

[reveman, 2015/08/21 18:05:24]

nit: !span->shared_memory()

[ssid, 2015/08/24 14:52:10]

Done.

+    return nullptr;
+
+  base::trace_event::MemoryAllocatorDump* allocator_dump;
+  std::for_each(

[reveman, 2015/08/21 18:05:24]

can you instead do a std:::find_if for span->shared_memory() and then create the
dump here instead of adding a ScopedMemorySegment function for it? as there
should only be one match..

[ssid, 2015/08/21 19:02:30]

I cannot do it because I have to match the span->shared_memory() with
ScopedMemorySegment::shared_memory_ : this is a private member and not exposed.
That is why I moved the implementation inside ScopedMemorySegment. I can either
expose the memory_segment and the id from ScopedMemorySegment, which will void
the purpose of the class, or get a callback from ScopedMemorySegment with
segment and id and create dump here. But creating there looked simpler.

[reveman, 2015/08/22 14:21:16]

How about adding a "bool ScopedMemorySegment::ContainsBlock(size_t start) const"
function? and keep ScopedMemorySegment::CreateMemoryAllocatorDump but remove the
"if (shared_memory_ != span->shared_memory())" check from it?

[ssid, 2015/08/22 14:50:19]

Yes I planned that at first, but I also need to add a subAllocation to the
segment, for which i need the segment id. That is why i moved the implementation
in there. If you want it to be implemented outside then I would have to make a
callback into the heap with id, if segment matches.

[reveman, 2015/08/22 15:04:07]

I was thinking you could use the ScopedMemorySegment::ContainsBlock to find the
correct segment and then use a ScopedMemorySegment::CreateMemoryAllocatorDump
function to create the dump. That function would have access to the id..

[ssid, 2015/08/22 15:13:00]

Ah sorry, I see what you meant now, sounds good, thanks

[ssid, 2015/08/24 14:52:10]

Done.

+      memory_segments_.begin(), memory_segments_.end(),
+      [span, name, pmd, &allocator_dump](const ScopedMemorySegment* segment) {
+        base::trace_event::MemoryAllocatorDump* dump =
+            segment->CreateMemoryAllocatorDump(span, name, pmd);
+        if (dump != nullptr)
+          allocator_dump = dump;
+      });
+
+  // Span with a shared memory should be found in some segment.
+  DCHECK(allocator_dump != nullptr);
+  return allocator_dump;
+}
+
 }  // namespace content