[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_memory_controller.h

+// Copyright 2016 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.
+
+#ifndef STORAGE_BROWSER_BLOB_BLOB_MEMORY_CONTROLLER_H_
+#define STORAGE_BROWSER_BLOB_BLOB_MEMORY_CONTROLLER_H_
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <list>
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/containers/mru_cache.h"
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "storage/browser/storage_browser_export.h"
+#include "storage/common/blob_storage/blob_storage_constants.h"
+
+namespace base {
+class TaskRunner;
+}
+
+namespace storage {
+class DataElement;
+class ShareableBlobDataItem;
+class ShareableFileReference;
+
+// There should be no memory sizes of 0.

[kinuko, 2016/07/17 16:15:46]

This sentence doesn't make a lot sense without context-- probably it's not the
best choice to start with for a class-level comment

[dmurph, 2016/07/19 02:26:27]

Done.

+// This class is responsible for
+// * our current memory usage for blobs, both on disk and in memory,
+// * when we can add a blob w/ a given size,
+// * creating temporary files,

[kinuko, 2016/07/17 16:15:46]

nit: now that we started to have a real 'temporary file', the term 'temporary
file item' used for future file blob item might start to feel unclear (the term
is used at least in blob_data_builder.h and in blob_slice.cc)

[dmurph, 2016/07/19 02:26:27]

Done.

+// * paging blobs to disk.
+class STORAGE_EXPORT BlobMemoryController {
+ public:
+  enum class MemoryStrategyResult {
+    // We don't have enough memory for this blob.
+    TOO_LARGE,
+    // There isn't any memory that needs transporting.
+    NONE_NEEDED,
+    // Transportation strategies.
+    IPC,
+    SHARED_MEMORY,
+    FILE
+  };
+  using PendingBlobConstructionList =
+      std::list<std::pair<size_t, base::Callback<void(bool)>>>;
+  using PendingConstructionEntry = PendingBlobConstructionList::iterator;
+
+  struct FileCreationInfo {
+    FileCreationInfo();
+    ~FileCreationInfo();
+    FileCreationInfo(FileCreationInfo&& other);
+    FileCreationInfo& operator=(FileCreationInfo&&);
+
+    base::File::Error error = base::File::FILE_ERROR_FAILED;
+    scoped_refptr<ShareableFileReference> file_reference;
+    base::File file;
+    base::Time last_modified;
+  };
+
+  BlobMemoryController();
+  virtual ~BlobMemoryController();
+
+  void EnableDisk(const base::FilePath& storage_directory,
+                  scoped_refptr<base::TaskRunner> file_runner);
+
+  // Disables the disk. This cancels all pending file creations and paging
+  // operations.
+  void DisableDisk();
+
+  bool disk_enabled() const { return disk_used_; }

[kinuko, 2016/07/17 16:15:46]

should this return enable_disk_ ??

[dmurph, 2016/07/19 02:26:27]

oops! Thanks.

+
+  // Returns if the data in the descriptions is good data (not a bad IPC).
+  bool DecideBlobTransportationMemoryStrategy(
+      const std::vector<DataElement>& descriptions,
+      uint64_t* total_bytes,
+      MemoryStrategyResult* result) const;
+
+  // Creates a temporary file that we store in our blob temporary directory. The
+  // lifetime of the file is tied to the file_reference. This method 'allocates'
+  // the disk memory right away.
+  // NOTE: We assume the user checked CanFitInSystem before this, as we don't
+  //       inspect quotas.
+  void CreateTemporaryFile(
+      uint64_t size_bytes,
+      const base::Callback<void(FileCreationInfo)>& file_callback);
+
+  void FreeMemory(size_t memory_size_bytes);
+
+  // Checks to see if the given size can fit in the system.
+  bool CanFitInSystem(uint64_t size) const;
+
+  // This method 'allocates' memory for the user, and we notify the caller when
+  // a blob of the given size can be stored in our blob system. If the returned
+  // entry is not present, that means the blob can fit right away and the
+  // callback won't be called. If we return a pending entry, then the memory
+  // isn't 'allocated' until |can_request| is called with true. IF the argument
+  // is false then there was an error and the new blob needs to be broken.
+  // NOTE: We assume the user checked CanFitInSystem before this, as we don't
+  //       inspect quotas.
+  base::Optional<PendingConstructionEntry> NotifyWhenMemoryCanPopulated(
+      size_t memory_size_bytes,
+      const base::Callback<void(bool)>& can_request);
+
+  // If we no longer need memory requsted from NotifyWhenMemoryCanPopulated
+  // before |can_request| has been called above, you can call this method to
+  // correctly free the requested memory.
+  void RemovePendingConstructionEntry(const PendingConstructionEntry& entry);
+
+  // This updates the given item in our LRU lookup table.
+  void UpdateBlobItemInRecents(ShareableBlobDataItem* item);
+
+  // This removes the given item from our LRU lookup table.
+  void RemoveBlobItemInRecents(const ShareableBlobDataItem& item);
+
+  size_t memory_usage() const {
+    return blob_memory_used_ + in_flight_memory_used_;
+  }
+  uint64_t disk_usage() const { return disk_used_; }
+
+  size_t max_ipc_memory_size() const { return max_ipc_memory_size_; }
+  size_t max_shared_memory_size() const { return max_shared_memory_size_; }
+  size_t max_blob_in_memory_size() const { return max_blob_in_memory_size_; }
+  uint64_t max_blob_disk_space() const { return max_blob_disk_space_; }
+  size_t in_flight_space() const { return in_flight_space_; }
+  uint64_t min_page_file_size() const { return min_page_file_size_; }
+  uint64_t max_file_size() const { return max_file_size_; }
+
+  void SetMemoryConstantsForTesting(size_t max_ipc_memory_size,
+                                    size_t max_shared_memory_size,
+                                    size_t max_blob_in_memory_size,
+                                    uint64_t max_blob_disk_space,
+                                    size_t in_flight_space,
+                                    uint64_t min_page_file_size,
+                                    uint64_t max_file_size) {
+    max_ipc_memory_size_ = max_ipc_memory_size;
+    max_shared_memory_size_ = max_shared_memory_size;
+    max_blob_in_memory_size_ = max_blob_in_memory_size;
+    max_blob_disk_space_ = max_blob_disk_space;
+    in_flight_space_ = in_flight_space;
+    min_page_file_size_ = min_page_file_size;
+    max_file_size_ = max_file_size;
+  }
+
+ private:
+  // We add a delete callback to the file reference to decrement our disk usage.
+  void OnCreateFile(uint64_t file_size,
+                    const base::Callback<void(FileCreationInfo)>& done,
+                    FileCreationInfo result);
+
+  void MaybeScheduleWaitingBlobs();
+
+  bool HasEnoughMemoryToPage() {
+    return recent_item_cache_bytes_ >= min_page_file_size_;
+  }
+
+  // We schedule paging for all memory over our in memory limit, including
+  // any memory waiting to be allocated. We appropriately increment/decrement
+  // the disk, memory, and in flight counts.
+  void MaybeSchedulePagingUntilSystemHealthy();
+
+  // Called when we've completed paging a list of items
+  void OnPagingComplete(
+      std::unique_ptr<std::vector<scoped_refptr<ShareableBlobDataItem>>> items,
+      size_t total_items_size,
+      FileCreationInfo result);
+
+  void RecordTracingCounters();
+
+  size_t GetAvailableMemoryForBlobs() const;
+  uint64_t GetAvailableDiskSpaceForBlobs() const;
+
+  // We decrement the disk space used.
+  void OnBlobFileDelete(uint64_t size, const base::FilePath& path);
+
+  // Memory bookkeeping.

[kinuko, 2016/07/17 16:15:46]

Please add more comments for bookkeeping fields.

[dmurph, 2016/07/19 02:26:27]

Done.

+  size_t blob_memory_used_ = 0;
+  size_t in_flight_memory_used_ = 0;
+  uint64_t disk_used_ = 0;
+
+  scoped_refptr<base::TaskRunner> file_runner_;

[kinuko, 2016/07/17 16:15:46]

Move this above or below other memory bookkeeping stuff (if it doesn't need to
be in particular order for destruction)

[dmurph, 2016/07/19 02:26:27]

Done.

+
+  size_t pending_pagings_ = 0;
+  PendingBlobConstructionList blobs_waiting_for_paging_;
+  size_t blobs_waiting_for_paging_size_ = 0;
+
+  // Constants.
+  // TODO(dmurph): consolidate these into a struct.
+  size_t max_ipc_memory_size_ = kBlobStorageIPCThresholdBytes;
+  size_t max_shared_memory_size_ = kBlobStorageMaxSharedMemoryBytes;
+  size_t max_blob_in_memory_size_ = kBlobStorageMaxBlobMemorySize;
+  uint64_t max_blob_disk_space_ = kBlobStorageMaxDiskSpace;
+  size_t in_flight_space_ = kBlobStorageInFlightMemory;

[kinuko, 2016/07/17 16:15:46]

nit: why some are called 'space' while others are called 'memory size' ?

Can these (or the constants) have a little more comments?

[dmurph, 2016/07/19 02:26:27]

Done.

+  uint64_t min_page_file_size_ = kBlobStorageMinFileSizeBytes;
+  uint64_t max_file_size_ = kBlobStorageMaxFileSizeBytes;
+
+  bool enable_disk_ = false;

[kinuko, 2016/07/17 16:15:46]

disk_enabled_ ??

[dmurph, 2016/07/19 02:26:27]

Done.

+  base::FilePath blob_storage_dir_;
+  uint64_t current_file_num_ = 0;
+
+  // Lifetime of the ShareableBlobDataItem objects is handled externally in the
+  // BlobStorageContext class.
+  base::MRUCache<uint64_t, ShareableBlobDataItem*> recent_item_cache_;
+  size_t recent_item_cache_bytes_ = 0;
+
+  base::WeakPtrFactory<BlobMemoryController> ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobMemoryController);
+};
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_MEMORY_CONTROLLER_H_