[tracing]Fix resident size of malloc for mac and ios.

base/trace_event/malloc_dump_provider.cc

 // Copyright 2015 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 "base/trace_event/malloc_dump_provider.h"
 
 #if defined(OS_MACOSX)
 #include <malloc/malloc.h>
 #else
 #include <malloc.h>
@@ skipping 18 matching lines @@
 
 MallocDumpProvider::~MallocDumpProvider() {}
 
 // Called at trace dump point time. Creates a snapshot the memory counters for
 // the current process.
 bool MallocDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
                                       ProcessMemoryDump* pmd) {
   size_t total_virtual_size = 0;
   size_t resident_size = 0;
   size_t allocated_objects_size = 0;
-#if defined(OS_MACOSX) || defined(OS_IOS)
-  malloc_statistics_t stats = {0};
-  malloc_zone_statistics(nullptr, &stats);
-  total_virtual_size = stats.size_allocated;
-  resident_size = stats.size_in_use;
-  allocated_objects_size = stats.size_in_use;
-#elif defined(USE_TCMALLOC)
+#if defined(USE_TCMALLOC)
   bool res =
       allocator::GetNumericProperty("generic.heap_size", &total_virtual_size);
   DCHECK(res);
   res = allocator::GetNumericProperty("generic.total_physical_bytes",
                                       &resident_size);
   DCHECK(res);
   res = allocator::GetNumericProperty("generic.current_allocated_bytes",
                                       &allocated_objects_size);
   DCHECK(res);
+#elif defined(OS_MACOSX) || defined(OS_IOS)
+  malloc_statistics_t stats = {0};
+  malloc_zone_statistics(nullptr, &stats);
+  total_virtual_size = stats.size_allocated;
+  allocated_objects_size = stats.size_in_use;
+
+  // The resident size is approximated to the max size in use, which would count
+  // the total size of all regions other than the free bytes at the end of each
+  // region. In each allocation region the allocations are rounded off to a
+  // fixed quantum, so the excess region will not be resident.
+  // See crrev.com/1531463004 for detailed explanation.
+  resident_size = stats.max_size_in_use;
 #else
   struct mallinfo info = mallinfo();
   DCHECK_GE(info.arena + info.hblkhd, info.uordblks);
 
   // In case of Android's jemalloc |arena| is 0 and the outer pages size is
   // reported by |hblkhd|. In case of dlmalloc the total is given by
   // |arena| + |hblkhd|. For more details see link: http://goo.gl/fMR8lF.
   total_virtual_size = info.arena + info.hblkhd;
   resident_size = info.uordblks;
   allocated_objects_size = info.uordblks;
 #endif
 
   MemoryAllocatorDump* outer_dump = pmd->CreateAllocatorDump("malloc");
   outer_dump->AddScalar("virtual_size", MemoryAllocatorDump::kUnitsBytes,
                         total_virtual_size);
   outer_dump->AddScalar(MemoryAllocatorDump::kNameSize,
                         MemoryAllocatorDump::kUnitsBytes, resident_size);
 
   // Total allocated space is given by |uordblks|.
   MemoryAllocatorDump* inner_dump = pmd->CreateAllocatorDump(kAllocatedObjects);
   inner_dump->AddScalar(MemoryAllocatorDump::kNameSize,
                         MemoryAllocatorDump::kUnitsBytes,
                         allocated_objects_size);
 
+  if (resident_size - allocated_objects_size > 0) {
+    // Explicitly specify why is extra memory resident. In tcmalloc it accounts
+    // for free lists and caches. In mac and ios it accounts for the
+    // fragmentation and metadata.
+    MemoryAllocatorDump* other_dump =
+        pmd->CreateAllocatorDump("malloc/metadata_fragmentation_caches");
+    other_dump->AddScalar(MemoryAllocatorDump::kNameSize,
+                          MemoryAllocatorDump::kUnitsBytes,
+                          resident_size - allocated_objects_size);
+  }
+
   return true;
 }
 
 }  // namespace trace_event
 }  // namespace base