Add DiscardableMemoryAllocator to work around FD limit issue.

base/memory/discardable_memory_allocator_android_unittest.cc

+// 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 <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include "base/logging.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) {
+  DCHECK_EQ(0U, memory->Size() % sizeof(int));
+  // Write to the first and the last pages only to avoid paging in up to 64
+  // MBytes.
+  static_cast<int*>(memory->Memory())[0] = 1;
+  static_cast<int*>(memory->Memory())[memory->Size() / sizeof(int) - 1] = 1;

[pasko, 2013/10/25 15:21:13]

if you wrote 'char', you would not have had to divide ..

Also, the style asks to prefer sizeof(varname) to sizeof(type), elimination
solves the preference choice problem.

[Philippe, 2013/10/28 09:44:43]

Yeah good point. I'm also a big supporter of sizeof(varname) (and even sizeof
with more complex expressions like function calls to do some advanced
compile-time dispatching) but here there was no variable to use :)

+}
+
+TEST_F(DiscardableMemoryAllocatorTest, Basic) {
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(128 * sizeof(int)));
+  ASSERT_TRUE(memory);
+  WriteToDiscardableMemory(memory.get());
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, LargeAllocation) {
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(64 * 1024 * 1024));
+  ASSERT_TRUE(memory);
+  WriteToDiscardableMemory(memory.get());
+}
+
+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());
+}
+
+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();
+  memory = allocator_.Allocate(kPageSize);
+  ASSERT_TRUE(memory);
+  // The previously freed chunk should be reused.
+  EXPECT_EQ(address, memory->Memory());
+  WriteToDiscardableMemory(memory.get());
+}
+
+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

[pasko, 2013/10/25 15:21:13]

Does this rely on the region having all chunks unlocked? If so, then this
precondition may unintentionally get broken later. The allocator is reused
between tests, so this depends on the order in which tests are run, since
previous tests could have leftover chunks. Frankly, I don't understand how it
works: the test AllocateFreeAllocate seems to leave a locked chunk behind.

[Philippe, 2013/10/28 09:44:43]

As we discussed offline GTest is full of (nice) surprises :) Each test case has
its own fixture class instance to provide some isolation.

+  // 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());
+}
+
+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();
+  memory1.reset(allocator_.Allocate(3 * kPageSize).release());
+  EXPECT_EQ(memory1_address, memory1->Memory());
+}
+
+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();
+  memory_2 = allocator_.Allocate(16 * 1024);
+  ASSERT_TRUE(memory_2);
+  EXPECT_EQ(address, memory_2->Memory());
+  WriteToDiscardableMemory(memory_2.get());
+  scoped_ptr<DiscardableMemory> memory_3(allocator_.Allocate(16 * 1024));
+  // The unused tail (16 KBytes large) of the previously freed chunk should be
+  // recycled.
+  EXPECT_EQ(static_cast<char*>(address) + memory_2->Size(), memory_3->Memory());
+  WriteToDiscardableMemory(memory_3.get());
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, UseMultipleAshmemRegions) {
+  // Leave one page untouched at the end of the ashmem region.
+  scoped_ptr<DiscardableMemory> memory1(
+      allocator_.Allocate(kMinAshmemRegionSize - kPageSize));
+  ASSERT_TRUE(memory1);
+  WriteToDiscardableMemory(memory1.get());
+
+  scoped_ptr<DiscardableMemory> memory2(
+      allocator_.Allocate(kMinAshmemRegionSize));
+  ASSERT_TRUE(memory2);
+  WriteToDiscardableMemory(memory2.get());
+  // The last page of the first ashmem region should be used for this
+  // allocation.

[pasko, 2013/10/25 15:21:13]

does ashmem guarantee the ranges of virtual addresses after each create? A
cleaner test would check that the address does not belong to the previous
region.

[Philippe, 2013/10/28 09:44:43]

I'm not sure I see what you mean here? :) The first ashmem region exists/is
mapped during the whole test.

[pasko, 2013/10/28 14:40:06]

sorry, please disregard, I misread the test

+  scoped_ptr<DiscardableMemory> memory3(allocator_.Allocate(kPageSize));
+  ASSERT_TRUE(memory3);
+  WriteToDiscardableMemory(memory3.get());
+  EXPECT_EQ(memory3->Memory(),
+            static_cast<char*>(memory1->Memory()) + memory1->Size());
+}
+
+// Returns -1 if an error happened during parsing.
+int GetAllocatorDirtyMemoryInKBytes() {

[pasko, 2013/10/25 15:21:13]

there is a similar function in disk_cache_memory_test.cc, did you consider
unifying these two and placing somewhere in base/memory/dirty_memory_posix.cc?

[Philippe, 2013/10/28 09:44:43]

Yeah, I think I will just remove this function and the test below TBH. Sorry for
the extra time you spent on it :/ I used to have this function to (incorrectly)
test that free chunks were uncommitted (by using madvise()). As I explained in a
comment in the .cc file, madvise(MADV_REMOVE) doesn't work unfortunately with
ashmem/on non-root devices and madvise(MADV_FREE) just makes us hide our actual
memory consumption as we used to do by unmapping the unpinned regions (please
see https://code.google.com/p/chromium/issues/detail?id=311633).

[pasko, 2013/10/28 14:40:06]

np! I am glad this ended up with less code :)

+  const std::string smaps_path = StringPrintf("/proc/%d/smaps", getpid());
+  std::ifstream stream(smaps_path.c_str());
+  if (!stream.good())
+    return -1;
+  std::vector<std::string> lines;
+  for (std::string line; std::getline(stream, line); lines.push_back(line));
+  int dirty_kbytes = 0;
+  for (std::vector<std::string>::const_iterator it = lines.begin();
+       it != lines.end(); ++it) {
+    if (it->find(kAllocatorName) == std::string::npos)
+      continue;
+    const std::string& private_dirty_line = it[7];
+    if (private_dirty_line.find("Private_Dirty") == std::string::npos)
+      return -1;
+    std::vector<std::string> tokens;
+    SplitString(private_dirty_line, ' ', &tokens);
+    if (tokens.size() < 3U)
+      return -1;
+    int size;
+    if (!base::StringToInt(tokens[tokens.size() - 2], &size))
+      return -1;
+    dirty_kbytes += size;
+    it += 6;

[pasko, 2013/10/25 15:21:13]

creating a vector of lines just to be able to skip 7 lines? I don't like it also
because the kernel might add more fields to report some day, why not just skip
until EOF or next range description?

+  }
+  return dirty_kbytes;
+}
+
+TEST_F(DiscardableMemoryAllocatorTest, PagesAreCommittedLazily) {
+  scoped_ptr<DiscardableMemory> memory(allocator_.Allocate(2 * 4096));
+  ASSERT_TRUE(memory);
+  EXPECT_EQ(0, GetAllocatorDirtyMemoryInKBytes());
+  static_cast<char*>(memory->Memory())[0] = 'a';
+  EXPECT_EQ(4, GetAllocatorDirtyMemoryInKBytes());

[pasko, 2013/10/25 15:21:13]

isn't this a subject to race conditions with /proc reporting?

[Philippe, 2013/10/28 09:44:43]

It's possible indeed if /proc reporting works by reading some metadata updated
asynchronously (which I don't know about). I will just remove this test. If
pages are not committed lazily then we have a serious problem :)

+  // Write to the second page.
+  static_cast<char*>(memory->Memory())[kPageSize] = 'b';
+  EXPECT_EQ(8, GetAllocatorDirtyMemoryInKBytes());
+}
+
+}  // namespace internal
+}  // namespace base