Add DiscardableMemoryAllocator to work around FD limit issue.

base/memory/discardable_memory_allocator_android_unittest.cc

Index: base/memory/discardable_memory_allocator_android_unittest.cc
diff --git a/base/memory/discardable_memory_allocator_android_unittest.cc b/base/memory/discardable_memory_allocator_android_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..153a2edbeb547bdfc131680dd34de1f017fe5d34
--- /dev/null
+++ b/base/memory/discardable_memory_allocator_android_unittest.cc
@@ -0,0 +1,209 @@
+// Copyright 2013 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/memory/discardable_memory_allocator_android.h"
+
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "base/memory/discardable_memory.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/stringprintf.h"
+#include "build/build_config.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace internal {
+
+const char kAllocatorName[] = "allocator-for-testing";
+
+const size_t kPageSize = 4096;
+const size_t kMinAshmemRegionSize =
+    DiscardableMemoryAllocator::kMinAshmemRegionSize;
+
+class DiscardableMemoryAllocatorTest : public testing::Test {
+ protected:
+  DiscardableMemoryAllocatorTest() : allocator_(kAllocatorName) {}
+
+  DiscardableMemoryAllocator allocator_;
+};
+
+void WriteToDiscardableMemory(DiscardableMemory* memory, size_t size) {
+  // Write to the first and the last pages only to avoid paging in up to 64
+  // MBytes.
+  static_cast<char*>(memory->Memory())[0] = 'a';
+  static_cast<char*>(memory->Memory())[size - 1] = 'a';
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, Basic) {
+  const size_t size = 128;
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(size));
+  ASSERT_TRUE(memory);
+  WriteToDiscardableMemory(memory.get(), size);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, LargeAllocation) {
+  const size_t size = 64 * 1024 * 1024;
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(size));
+  ASSERT_TRUE(memory);
+  WriteToDiscardableMemory(memory.get(), size);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, ChunksArePageAligned) {
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory);
+  EXPECT_EQ(0U, reinterpret_cast<uint64_t>(memory->Memory()) % kPageSize);
+  WriteToDiscardableMemory(memory.get(), kPageSize);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, AllocateFreeAllocate) {
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory);
+  void* const address = memory->Memory();
+  memory->Unlock();  // Tests that the recycled chunk is being locked correctly.
+  memory.reset();

[willchan no longer on Chromium, 2013/11/28 06:16:37]

It's not obvious to me why this shouldn't result in the AshmemRegion getting
deleted. After all, it now has 0 used chunks. It's true, it's only got one
FreeChunk, but the rest of the memory is not counted as a FreeChunk, but
|offset_| hasn't reached |base_| + |size_| yet. Is the intent here to keep
around the memory in case it gets reused? I thought we wanted to free as much
memory as possible when we can.

[Philippe, 2013/11/28 16:42:53]

You're right :) There was no reason not to delete the AshmemRegion. For some
reason my limited brain made me restrict the region deletion to the case where
the region gets full first and then gets empty (as
FreeingWholeAshmemRegionClosesAshmem testified below). Weird :)

+  memory = allocator_.Allocate(kPageSize);
+  ASSERT_TRUE(memory);
+  // The previously freed chunk should be reused.
+  EXPECT_EQ(address, memory->Memory());
+  WriteToDiscardableMemory(memory.get(), kPageSize);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, FreeingWholeAshmemRegionClosesAshmem) {
+  scoped_ptr<DiscardableMemory> memory(
+      allocator_.Allocate(kMinAshmemRegionSize));
+  ASSERT_TRUE(memory);
+  const int kMagic = 0xdeadbeef;
+  *static_cast<int*>(memory->Memory()) = kMagic;
+  memory.reset();
+  // The previous ashmem region should have been closed thus it should not be
+  // recycled.
+  memory = allocator_.Allocate(kPageSize);
+  ASSERT_TRUE(memory);
+  EXPECT_NE(kMagic, *static_cast<const int*>(memory->Memory()));
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, AllocateUsesBestFitAlgorithm) {
+  scoped_ptr<DiscardableMemory> memory1(allocator_.Allocate(3 * kPageSize));
+  ASSERT_TRUE(memory1);
+  scoped_ptr<DiscardableMemory> memory2(allocator_.Allocate(2 * kPageSize));
+  ASSERT_TRUE(memory2);
+  scoped_ptr<DiscardableMemory> memory3(allocator_.Allocate(1 * kPageSize));
+  ASSERT_TRUE(memory3);
+  void* const address_3 = memory3->Memory();
+  memory1.reset();
+  // Don't free |memory2| to avoid merging the 3 blocks together.
+  memory3.reset();
+  memory1 = allocator_.Allocate(1 * kPageSize);
+  ASSERT_TRUE(memory1);
+  // The chunk whose size is closest to the requested size should be recycled.
+  EXPECT_EQ(address_3, memory1->Memory());
+  WriteToDiscardableMemory(memory1.get(), kPageSize);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, MergeFreeChunks) {
+  scoped_ptr<DiscardableMemory> memory1(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory1);
+  scoped_ptr<DiscardableMemory> memory2(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory2);
+  scoped_ptr<DiscardableMemory> memory3(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory3);
+  void* const memory1_address = memory1->Memory();
+  memory1.reset();
+  memory3.reset();
+  // Freeing |memory2| (located between memory1 and memory3) should merge the
+  // three free blocks together.
+  memory2.reset();

[willchan no longer on Chromium, 2013/11/28 06:16:37]

Similar to above, it's not clear to me why this shouldn't kill the whole
AshmemRegion.

[Philippe, 2013/11/28 16:42:53]

Done.

+  memory1.reset(allocator_.Allocate(3 * kPageSize).release());

[willchan no longer on Chromium, 2013/11/28 06:16:37]

Why isn't this just memory1 = allocator_.Allocate(3 * kPageSize);

[Philippe, 2013/11/28 16:42:53]

Yeah, no idea why I wrote this :)

+  EXPECT_EQ(memory1_address, memory1->Memory());
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, MergeFreeChunksAdvanced) {
+  const size_t kHalfRegionSize = kMinAshmemRegionSize / 2;
+  const size_t kQuarterRegionSize = kMinAshmemRegionSize / 4;
+  scoped_ptr<DiscardableMemory> memory1(allocator_.Allocate(kHalfRegionSize));
+  ASSERT_TRUE(memory1);
+  scoped_ptr<DiscardableMemory> memory2(allocator_.Allocate(kHalfRegionSize));
+  ASSERT_TRUE(memory2);
+  void* const memory1_address = memory1->Memory();
+  memory1.reset();
+  memory1 = allocator_.Allocate(kQuarterRegionSize);
+  memory2.reset();
+  // At this point, the region should be in this state:
+  // 8 MBytes (used), 24 MBytes (free).
+  memory2 = allocator_.Allocate(kMinAshmemRegionSize - kQuarterRegionSize);
+  EXPECT_EQ(
+      static_cast<const char*>(memory2->Memory()),
+      static_cast<const char*>(memory1_address) + kQuarterRegionSize);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, MergeFreeChunksAdvanced2) {
+  const size_t kHalfRegionSize = kMinAshmemRegionSize / 2;
+  const size_t kQuarterRegionSize = kMinAshmemRegionSize / 4;
+  scoped_ptr<DiscardableMemory> memory1(allocator_.Allocate(kHalfRegionSize));
+  ASSERT_TRUE(memory1);
+  scoped_ptr<DiscardableMemory> memory2(allocator_.Allocate(kHalfRegionSize));
+  ASSERT_TRUE(memory2);
+  void* const memory1_address = memory1->Memory();
+  memory1.reset();
+  memory1 = allocator_.Allocate(kQuarterRegionSize);
+  scoped_ptr<DiscardableMemory> memory3(
+      allocator_.Allocate(kQuarterRegionSize));
+  // At this point, the region should be in this state:
+  // 8 MBytes (used), 8 MBytes (used), 16 MBytes (used).
+  memory3.reset();
+  memory2.reset();
+  // At this point, the region should be in this state:
+  // 8 MBytes (used), 24 MBytes (free).
+  memory2 = allocator_.Allocate(kMinAshmemRegionSize - kQuarterRegionSize);
+  EXPECT_EQ(
+      static_cast<const char*>(memory2->Memory()),
+      static_cast<const char*>(memory1_address) + kQuarterRegionSize);
+}

[willchan no longer on Chromium, 2013/11/28 06:16:37]

It'd be cool if you added a third one of these where you ended up with: free,
used, free.
When you freed the used chunk, that'd merge all of them, and then also delete
the entire AshmemRegion.

[Philippe, 2013/11/28 16:42:53]

Yeah, good idea. Done.

+
+TEST_F(DiscardableMemoryAllocatorTest,
+     TooLargeFreeChunksDontCauseTooMuchFragmentationWhenRecycled) {
+  // Keep |memory_1| below allocated so that the ashmem region doesn't get
+  // closed when |memory_2| is deleted.
+  scoped_ptr<DiscardableMemory> memory_1(allocator_.Allocate(64 * 1024));
+  ASSERT_TRUE(memory_1);
+  scoped_ptr<DiscardableMemory> memory_2(allocator_.Allocate(32 * 1024));
+  ASSERT_TRUE(memory_2);
+  void* const address = memory_2->Memory();
+  memory_2.reset();
+  const size_t size = 16 * 1024;
+  memory_2 = allocator_.Allocate(size);
+  ASSERT_TRUE(memory_2);
+  EXPECT_EQ(address, memory_2->Memory());
+  WriteToDiscardableMemory(memory_2.get(), size);
+  scoped_ptr<DiscardableMemory> memory_3(allocator_.Allocate(size));
+  // The unused tail (16 KBytes large) of the previously freed chunk should be
+  // recycled.
+  EXPECT_EQ(static_cast<char*>(address) + size, memory_3->Memory());
+  WriteToDiscardableMemory(memory_3.get(), size);
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, UseMultipleAshmemRegions) {
+  // Leave one page untouched at the end of the ashmem region.
+  const size_t size = kMinAshmemRegionSize - kPageSize;
+  scoped_ptr<DiscardableMemory> memory1(allocator_.Allocate(size));
+  ASSERT_TRUE(memory1);
+  WriteToDiscardableMemory(memory1.get(), size);
+
+  scoped_ptr<DiscardableMemory> memory2(
+      allocator_.Allocate(kMinAshmemRegionSize));
+  ASSERT_TRUE(memory2);
+  WriteToDiscardableMemory(memory2.get(), kMinAshmemRegionSize);
+  // The last page of the first ashmem region should be used for this
+  // allocation.
+  scoped_ptr<DiscardableMemory> memory3(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory3);
+  WriteToDiscardableMemory(memory3.get(), kPageSize);
+  EXPECT_EQ(memory3->Memory(), static_cast<char*>(memory1->Memory()) + size);
+}
+
+}  // namespace internal
+}  // namespace base