Use DiscardableMemoryManager on Android.

base/memory/discardable_memory_android.cc

Index: base/memory/discardable_memory_android.cc
diff --git a/base/memory/discardable_memory_android.cc b/base/memory/discardable_memory_android.cc
index fa89c189db7be5170ecf30ea3a2a882c24fc87db..9ef08ac858dea98fe31c1d9d7314171b6eba455d 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -10,6 +10,7 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/discardable_memory_allocator_android.h"
+#include "base/memory/discardable_memory_ashmem.h"
 #include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/discardable_memory_malloc.h"
 
@@ -18,13 +19,22 @@ namespace {
 
 const char kAshmemAllocatorName[] = "DiscardableMemoryAllocator";
 
-struct DiscardableMemoryAllocatorWrapper {
-  DiscardableMemoryAllocatorWrapper()
+// When ashmem is used, have the DiscardableMemoryManager trigger userspace
+// eviction when address space usage gets too high, e.g. 512 MBytes on 32 bit
+// systems vs 16 GBytes on 64 bits.
+const size_t kAshmemMaxAddressSpaceUsage =
+    ((sizeof(void*) == 4) ? 512 : 16 * 1024) * 1024 * 1024;

[reveman, 2014/04/26 00:13:37]

I would prefer if used the same constant on 64bit to start with. 512MB is fine
if that's the highest you think we should use on 32bit.

[Philippe, 2014/04/28 12:23:14]

Done.

+
+// Holds the state used for ashmem allocations.
+struct AshmemGlobalContext {
+  AshmemGlobalContext()
       : allocator(kAshmemAllocatorName,
                   GetOptimalAshmemRegionSizeForAllocator()) {
+    manager.SetMemoryLimit(kAshmemMaxAddressSpaceUsage);
   }
 
   internal::DiscardableMemoryAllocator allocator;
+  internal::DiscardableMemoryManager manager;
 
  private:
   // Returns 64 MBytes for a 512 MBytes device, 128 MBytes for 1024 MBytes...
@@ -35,8 +45,7 @@ struct DiscardableMemoryAllocatorWrapper {
   }
 };
 
-LazyInstance<DiscardableMemoryAllocatorWrapper>::Leaky g_context =
-    LAZY_INSTANCE_INITIALIZER;
+LazyInstance<AshmemGlobalContext>::Leaky g_context = LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
@@ -69,7 +78,14 @@ scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
     case DISCARDABLE_MEMORY_TYPE_MAC:
       return scoped_ptr<DiscardableMemory>();
     case DISCARDABLE_MEMORY_TYPE_ANDROID: {
-      return g_context.Pointer()->allocator.Allocate(size);
+      AshmemGlobalContext* const global_context = g_context.Pointer();
+      scoped_ptr<internal::DiscardableMemoryAshmem> memory(
+          new internal::DiscardableMemoryAshmem(
+              size, &global_context->allocator, &global_context->manager));
+      if (!memory->Initialize())
+        return scoped_ptr<DiscardableMemory>();
+
+      return memory.PassAs<DiscardableMemory>();
     }
     case DISCARDABLE_MEMORY_TYPE_EMULATED: {
       scoped_ptr<internal::DiscardableMemoryEmulated> memory(