Global GPU memory manager for android webview

android_webview/browser/global_tile_manager.h

+// Copyright 2014 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 ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_
+#define ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_
+
+#include <list>
+#include "base/basictypes.h"
+#include "base/lazy_instance.h"
+#include "base/sequence_checker.h"
+#include "base/synchronization/lock.h"
+
+namespace android_webview {
+
+class GlobalTileManagerClient;
+
+// A global tile manager that keeps track of the number of tile resources. Each
+// tile needs file descriptors (typically 2) and there is a soft limit of 1024
+// file descriptors per Android process. The GlobalTileManager does not keep
+// track of how many tiles each individual view is actually using. The purpose
+// of GlobalTileManager is to behave gracefully (as in not crashing) when the
+// embedder of webview creates a lot of webviews and draw them at the same time.
+class GlobalTileManager {
+ private:
+  typedef std::list<GlobalTileManagerClient*> ListType;
+
+ public:
+  typedef ListType::iterator Key;
+  static GlobalTileManager* GetInstance();
+
+  // Requests the |num_of_tiles| from the available global pool. Calls
+  // GlobalTileManagerClient.SetNumTiles after the manager determines how many
+  // tiles are available for the client. The tile policy on the clients are not
+  // immediately enforced, unless |effective_immediately| is true. If the
+  // number of tiles left are not enough to satisfy the request, the manager
+  // will evict tiles allocated to other clients.
+  void RequestTiles(size_t new_num_of_tiles,
+                    bool effective_immediately,
+                    Key key);
+
+  Key PushBack(GlobalTileManagerClient* client);
+
+  // |key| must be already in manager. Move the tile manager client
+  // corresponding to |key| to most recent. This function should be called after
+  // RequestTiles.
+  void DidUse(Key key);
+
+  void Remove(Key key);
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<GlobalTileManager>;
+  GlobalTileManager();
+  ~GlobalTileManager();
+
+  // Continues evicting the inactive views until freeing up at least amount of
+  // tiles specified by |desired_num_tiles| to draw a view specified by |key|,
+  // or until all inactive views have been evicted. Returns the amount of
+  // memory that was actually evicted. This function is called when a
+  // request cannot be satisfied.
+  size_t Evict(size_t desired_num_tiles, Key key);
+
+  // Check that the sum of all client's tiles is equal to
+  // total_allocated_tiles_.
+  bool IsConsistent() const;
+
+  size_t total_allocated_tiles_;
+  ListType mru_list_;
+  base::SequenceChecker sequence_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(GlobalTileManager);
+};
+
+}  // namespace android_webview
+
+#endif  // ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_