Adding discardable memory dump provider.

content/common/discardable_shared_memory_heap.h

 // 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.
 
 #ifndef CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
 #define CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/containers/linked_list.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "content/common/content_export.h"
 
 namespace base {
 class DiscardableSharedMemory;
 }
 
 namespace content {
 
 // Implements a heap of discardable shared memory. An array of free lists
 // is used to keep track of free blocks.
@@ skipping 53 matching lines @@
 
   // Release shared memory segments that have been purged.
   void ReleasePurgedMemory();
 
   // Returns total bytes of memory in heap.
   size_t GetSize() const;
 
   // Returns bytes of memory currently in the free lists.
   size_t GetSizeOfFreeLists() const;
 
+  // Dumps memory statistics for chrome://tracing.
+  bool DumpMemoryStatisticsInto(base::trace_event::ProcessMemoryDump* pmd);
+
  private:
   class ScopedMemorySegment {
    public:
     ScopedMemorySegment(DiscardableSharedMemoryHeap* heap,
                         scoped_ptr<base::DiscardableSharedMemory> shared_memory,
                         size_t size,
                         const base::Closure& deleted_callback);
     ~ScopedMemorySegment();
 
     bool IsUsed() const;
     bool IsResident() const;
 
    private:
+    friend class DiscardableSharedMemoryHeap;

[reveman, 2015/04/24 14:19:36]

hm, sorry I missed this in my previous review. What do you think about removing
this friend class and instead add a public DumpInto() function that just calls
heap_->DumpMemoryInto(shared_memory_.get(), size_, id_)? It's not ideal to have
this type of indirection but that's what we have for IsUsed, IsResident so I
think it would be the most consistent way to implement this right now.

[ssid, 2015/04/27 11:19:21]

Yes, I tried to explain this indirection in last patch, I wasn't clear. made
changes now.

+
     DiscardableSharedMemoryHeap* const heap_;
     scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
     const size_t size_;

[reveman, 2015/04/24 14:19:36]

I think we should add "const DiscardableSharedMemoryId id_;" here and use that
as segment id. This id is unique and won't change between dumps like the vector
index.

[ssid, 2015/04/27 11:19:21]

Done.

     const base::Closure deleted_callback_;
 
     DISALLOW_COPY_AND_ASSIGN(ScopedMemorySegment);
   };
 
   void InsertIntoFreeList(scoped_ptr<Span> span);
   scoped_ptr<Span> RemoveFromFreeList(Span* span);
   scoped_ptr<Span> Carve(Span* span, size_t blocks);
   void RegisterSpan(Span* span);
   void UnregisterSpan(Span* span);
   bool IsMemoryUsed(const base::DiscardableSharedMemory* shared_memory,
                     size_t size);
   bool IsMemoryResident(const base::DiscardableSharedMemory* shared_memory);
   void ReleaseMemory(const base::DiscardableSharedMemory* shared_memory,
                      size_t size);

[reveman, 2015/04/24 14:19:36]

to do what I suggested above we'd need something like this here:

void DumpMemoryInto(const base::DiscardableSharedMemory* shared_memory,
                    size_t size,
                    DiscardableSharedMemoryId id);

[ssid, 2015/04/27 11:19:21]

Also with ProcessMemoryDump* .

 
   size_t block_size_;
   size_t num_blocks_;
   size_t num_free_blocks_;
 
   // Vector of memory segments.
   ScopedVector<ScopedMemorySegment> memory_segments_;
 
   // Mapping from first/last block of span to Span instance.
   typedef base::hash_map<size_t, Span*> SpanMap;
   SpanMap spans_;
 
   // Array of linked-lists with free discardable memory regions. For i < 256,
   // where the 1st entry is located at index 0 of the array, the kth entry
   // is a free list of runs that consist of k blocks. The 256th entry is a
   // free list of runs that have length >= 256 blocks.
   base::LinkedList<Span> free_spans_[256];
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableSharedMemoryHeap);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_