Add DiscardableMemoryAllocator to work around FD limit issue.

base/memory/discardable_memory_allocator_android.cc

Index: base/memory/discardable_memory_allocator_android.cc
diff --git a/base/memory/discardable_memory_allocator_android.cc b/base/memory/discardable_memory_allocator_android.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a212f2b853f836499f2e58bba1e09a737330b133
--- /dev/null
+++ b/base/memory/discardable_memory_allocator_android.cc
@@ -0,0 +1,284 @@
+// Copyright (c) 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.h"
+
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <cmath>
+#include <set>
+#include <utility>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/containers/hash_tables.h"
+#include "base/logging.h"
+#include "base/memory/discardable_memory.h"
+#include "base/memory/discardable_memory_android.h"
+#include "base/memory/linked_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "base/strings/stringprintf.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/platform_thread.h"
+#include "base/threading/thread_checker.h"
+
+namespace base {
+namespace {
+
+const size_t kDefaultAshmemRegionSize = 32 * 1024 * 1024;
+
+size_t PageAlign(size_t size, size_t page_size) {
+  const size_t mask = ~(page_size - 1);
+  return (size + page_size - 1) & mask;
+}
+
+class DiscardableMemoryChunk : public DiscardableMemory {
+ public:
+  struct DeletionObserver {
+    virtual void OnChunkDeletion(void* addr, size_t size, bool locked) = 0;
+  };
+
+  DiscardableMemoryChunk(DeletionObserver* deletion_observer,
+                         int fd,
+                         void* address,
+                         size_t offset,
+                         size_t client_requested_size,
+                         size_t actual_size)
+      : DiscardableMemory(client_requested_size),
+        deletion_observer_(deletion_observer),
+        fd_(fd),
+        address_(address),
+        offset_(offset),
+        size_(actual_size),
+        locked_(true) {
+  }
+
+  virtual ~DiscardableMemoryChunk() {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    if (locked_)
+      Unlock();
+    deletion_observer_->OnChunkDeletion(address_, size_, locked_);
+  }
+
+  // DiscardableMemory:
+  virtual LockDiscardableMemoryStatus Lock() OVERRIDE {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    locked_ = true;
+    return internal::LockAshmemRegion(fd_, offset_, size_, address_);
+  }
+
+  virtual void Unlock() OVERRIDE {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    locked_ = false;
+    internal::UnlockAshmemRegion(fd_, offset_, size_, address_);
+  }
+
+  virtual void* Memory() const OVERRIDE {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    DCHECK(locked_);
+    return address_;
+  }
+
+ private:
+  base::ThreadChecker thread_checker_;
+  DeletionObserver* const deletion_observer_;
+  const int fd_;
+  void* const address_;
+  const size_t offset_;
+  const size_t size_ : sizeof(size_t) * 8 - 1;
+  bool locked_ : 1;
+
+  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryChunk);
+};
+
+class AshmemRegion : public DiscardableMemoryChunk::DeletionObserver {
+ public:
+  ~AshmemRegion() {
+    const bool result = internal::DeleteAshmemRegion(fd_, size_, base_);
+    DCHECK(result);
+  }
+
+  // DiscardableMemoryChunk::DeletionObserver:
+  virtual void OnChunkDeletion(void* addr, size_t size, bool locked) OVERRIDE {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    free_chunks_.insert(FreeChunk(addr, size, locked));
+    // Keep the chunk mapped but let the kernel know that it can immediately
+    // release the underlying physical pages.
+    const int result = madvise(addr, size, MADV_DONTNEED);
+    DCHECK_NE(-1, result);
+  }
+
+  static scoped_ptr<AshmemRegion> Create(size_t size, const char* name) {
+    int fd;
+    void* address;
+    if (!internal::CreateAshmemRegion(name, size, &fd, &address))
+      return scoped_ptr<AshmemRegion>();
+    return make_scoped_ptr(new AshmemRegion(fd, address, size));
+  }
+
+  scoped_ptr<DiscardableMemory> Allocate(size_t client_requested_size,
+                                         size_t actual_size) {
+    const std::multiset<FreeChunk>::iterator chunk_it =
+        free_chunks_.lower_bound(FreeChunk(NULL, actual_size, false));
+    if (chunk_it != free_chunks_.end()) {
+      const int result = madvise(chunk_it->start, chunk_it->size, MADV_NORMAL);
+      DCHECK_NE(-1, result);
+      const size_t offset =
+          static_cast<char*>(chunk_it->start) - static_cast<char*>(base_);
+      if (!chunk_it->locked) {
+        // Lock the chunk being recycled if it was left in an unlocked state.
+        internal::LockAshmemRegion(
+            fd_, offset, chunk_it->size, chunk_it->start);
+      }
+      scoped_ptr<DiscardableMemory> memory(
+          new DiscardableMemoryChunk(this, fd_, chunk_it->start, offset,
+                                     client_requested_size, actual_size));
+      free_chunks_.erase(chunk_it);
+      return memory.Pass();
+    }
+    if (size_ - offset_ < actual_size) {
+      // This region does not have enough space left to hold the requested size.
+      return scoped_ptr<DiscardableMemory>();
+    }
+    void* const address = static_cast<char*>(base_) + offset_;
+    scoped_ptr<DiscardableMemory> memory(
+        new DiscardableMemoryChunk(
+            this, fd_, address, offset_, client_requested_size, actual_size));
+    offset_ += actual_size;
+    return memory.Pass();
+  }
+
+ private:
+  struct FreeChunk {
+    FreeChunk(void* start, size_t size, bool locked)
+        : start(start),
+          size(size),
+          locked(locked) {
+    }
+
+    void* const start;
+    const size_t size : sizeof(size_t) * 8 - 1;
+    const bool locked : 1;
+
+    bool operator<(const FreeChunk& other) const {
+      return size < other.size;
+    }
+  };
+
+  AshmemRegion(int fd, void* base, size_t size)
+      : fd_(fd),
+        base_(base),
+        size_(size),
+        offset_(0) {
+  }
+
+  const int fd_;
+  void* const base_;
+  const size_t size_;
+  size_t offset_;
+  std::multiset<FreeChunk> free_chunks_;
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(AshmemRegion);
+};
+
+class DiscardableMemoryAllocatorAndroid : public DiscardableMemoryAllocator {
+ public:
+  DiscardableMemoryAllocatorAndroid(const std::string& name)
+      : page_size_(getpagesize()),
+        name_(name) {
+  }
+
+  virtual ~DiscardableMemoryAllocatorAndroid() {
+    DCHECK(thread_checker_.CalledOnValidThread());
+  }
+
+  // DiscardableMemoryAllocator:
+  virtual scoped_ptr<DiscardableMemory> Allocate(size_t size) OVERRIDE {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    const size_t aligned_size = PageAlign(size, page_size_);
+    for (ScopedVector<AshmemRegion>::iterator it = ashmem_regions_.begin();
+         it != ashmem_regions_.end(); ++it) {
+      scoped_ptr<DiscardableMemory> memory((*it)->Allocate(size, aligned_size));
+      if (memory)
+        return memory.Pass();
+    }
+    scoped_ptr<AshmemRegion> ashmem_region = AshmemRegion::Create(
+        std::max(kDefaultAshmemRegionSize, aligned_size), name_.c_str());
+    if (!ashmem_region)
+      return scoped_ptr<DiscardableMemory>();
+
+    ashmem_regions_.push_back(ashmem_region.release());
+    return ashmem_regions_.back()->Allocate(size, aligned_size);
+  }
+
+ private:
+  const size_t page_size_;
+  const std::string name_;
+  ScopedVector<AshmemRegion> ashmem_regions_;
+  base::ThreadChecker thread_checker_;
+};
+
+// Stores per-thread allocator instances and dispatches allocations to them.
+// Note that not sharing free chunks across threads doesn't increase the overall
+// memory footprint since free chunks are not committed.
+class ThreadSafeAllocatorWrapper : public DiscardableMemoryAllocator {
+  public:
+   ThreadSafeAllocatorWrapper(const std::string& name) : name_(name) {}
+
+   // DiscardableMemoryAllocator:
+   virtual scoped_ptr<DiscardableMemory> Allocate(size_t size) OVERRIDE {
+     const base::PlatformThreadId thread_id = base::PlatformThread::CurrentId();
+     DiscardableMemoryAllocatorAndroid* thread_allocator = NULL;
+     {
+       const base::AutoLock auto_lock(lock_);
+       const std::pair<
+           base::hash_map<
+               base::PlatformThreadId,
+               linked_ptr<DiscardableMemoryAllocatorAndroid> >::iterator,
+           bool> result =
+               per_thread_allocators_.insert(
+                   std::make_pair(
+                       thread_id,
+                       linked_ptr<DiscardableMemoryAllocatorAndroid>(NULL)));
+       const bool did_insert = result.second;
+       if (did_insert) {
+         result.first->second.reset(
+             new DiscardableMemoryAllocatorAndroid(
+                 base::StringPrintf("%s-Thread-%d", name_.c_str(), thread_id)));
+       }
+       thread_allocator = result.first->second.get();
+     }
+     return thread_allocator->Allocate(size);
+   }
+
+  private:
+   const std::string name_;
+   // Protects the hash_map below.
+   base::Lock lock_;
+   // Stores one allocator per thread.
+   base::hash_map<
+       base::PlatformThreadId,
+       linked_ptr<DiscardableMemoryAllocatorAndroid> > per_thread_allocators_;
+
+   DISALLOW_COPY_AND_ASSIGN(ThreadSafeAllocatorWrapper);
+};
+
+}  // namespace
+
+scoped_ptr<DiscardableMemoryAllocator> DiscardableMemoryAllocator::Create(
+    const std::string& name) {
+  return scoped_ptr<DiscardableMemoryAllocator>(
+      new DiscardableMemoryAllocatorAndroid(name));
+}
+
+scoped_ptr<DiscardableMemoryAllocator>
+DiscardableMemoryAllocator::CreateThreadSafeInstance(
+    const std::string& name) {
+  return scoped_ptr<DiscardableMemoryAllocator>(
+      new ThreadSafeAllocatorWrapper(name));
+}
+
+}  // namespace base