[BlobStorage] Enabling disk paging and direct storage.

storage/common/blob_storage/blob_storage_constants.h

 // Copyright 2015 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_COMMON_BLOB_STORAGE_BLOB_STORAGE_CONSTANTS_H_
 #define STORAGE_COMMON_BLOB_STORAGE_BLOB_STORAGE_CONSTANTS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/callback_forward.h"
 #include "storage/common/storage_common_export.h"
 
 namespace storage {
 
+constexpr size_t kDefaultIPCMemorySize = 250u * 1024;
+constexpr size_t kDefaultSharedMemorySize = 10u * 1024 * 1024;
+constexpr size_t kDefaultMaxBlobInMemorySpace = 500u * 1024 * 1024;
+constexpr uint64_t kDefaultMaxBlobDiskSpace = 0ull;
+constexpr uint64_t kDefaultMinPageFileSize = 5ull * 1024 * 1024;
+constexpr uint64_t kDefaultMaxPageFileSize = 100ull * 1024 * 1024;
+
 // All sizes are in bytes.
-struct BlobStorageLimits {
+struct STORAGE_COMMON_EXPORT BlobStorageLimits {
+  // Returns if the current configuration is valid.
+  bool IsValid() const;
+
   size_t memory_limit_before_paging() const {
     return max_blob_in_memory_space - min_page_file_size;
   }
 
+  // If disk space goes less than this we stop allocating more disk quota.
+  uint64_t min_available_disk_space() const {
+    return 2ull * memory_limit_before_paging();

[michaeln, 2016/12/08 21:17:33]

why is this number a function of the mem limit? unless there's a good reason, i
think a datamember that defaults to a hardcoded value would be easier to grok
and work with

[dmurph, 2016/12/20 02:21:36]

It's basically because memory_limit_before_paging() is the minimum size of a
file that's being sent straight to disk - where we ask for new empty files. So I
wanted to do a multiple of that. I can make this multiple higher. WDYT?

+  }
+
   // This is the maximum amount of memory we can send in an IPC.
-  size_t max_ipc_memory_size = 250 * 1024;
+  size_t max_ipc_memory_size = kDefaultIPCMemorySize;
   // This is the maximum size of a shared memory handle.
-  size_t max_shared_memory_size = 10 * 1024 * 1024;
+  size_t max_shared_memory_size = kDefaultSharedMemorySize;
 
   // This is the maximum amount of memory we can use to store blobs.
-  size_t max_blob_in_memory_space = 500 * 1024 * 1024;
+  size_t max_blob_in_memory_space = kDefaultMaxBlobInMemorySpace;
 
   // This is the maximum amount of disk space we can use.
   // TODO(dmurph): Determine initial heuristic based on disk usage & arch.
-  uint64_t max_blob_disk_space = 0ull;
+  uint64_t max_blob_disk_space = kDefaultMaxBlobDiskSpace;
 
   // This is the minimum file size we can use when paging blob items to disk.
   // We combine items until we reach at least this size.
-  uint64_t min_page_file_size = 5 * 1024 * 1024;
+  uint64_t min_page_file_size = kDefaultMinPageFileSize;
   // This is the maximum file size we can create.
-  uint64_t max_file_size = 100 * 1024 * 1024;
+  uint64_t max_file_size = kDefaultMaxPageFileSize;
 };
 
 enum class IPCBlobItemRequestStrategy {
   UNKNOWN = 0,
   IPC,
   SHARED_MEMORY,
   FILE,
   LAST = FILE
 };
 
@@ skipping 42 matching lines @@
 
 STORAGE_COMMON_EXPORT bool BlobStatusIsPending(BlobStatus status);
 
 // Returns if the status is a bad enough error to flag the IPC as bad. This is
 // only INVALID_CONSTRUCTION_ARGUMENTS.
 STORAGE_COMMON_EXPORT bool BlobStatusIsBadIPC(BlobStatus status);
 
 }  // namespace storage
 
 #endif  // STORAGE_COMMON_BLOB_STORAGE_BLOB_STORAGE_CONSTANTS_H_