1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_ 6 #define ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_ 7 8 #include <list> 9 #include "base/basictypes.h" 10 #include "base/lazy_instance.h" 11 #include "base/sequence_checker.h" 12 #include "base/synchronization/lock.h" 13 14 namespace android_webview { 15 16 class GlobalTileManagerClient; 17 18 // A global tile manager that keeps track of the number of tile resources. Each 19 // tile needs file descriptors (typically 2) and there is a soft limit of 1024 20 // file descriptors per Android process. The GlobalTileManager does not keep 21 // track of how many tiles each individual view is actually using. The purpose 22 // of GlobalTileManager is to behave gracefully (as in not crashing) when the 23 // embedder of webview creates a lot of webviews and draw them at the same time. 24 class GlobalTileManager { 25 private: 26 typedef std::list<GlobalTileManagerClient*> ListType; 27 28 public: 29 typedef ListType::iterator Key; 30 static GlobalTileManager* GetInstance(); 31 32 void SetTileLimit(size_t num_tiles_limit); 33 34 // Requests the |new_num_of_tiles| from the available global pool. Calls 35 // GlobalTileManagerClient.SetNumTiles after the manager determines how many 36 // tiles are available for the client. If the number of tiles left is not 37 // enough to satisfy the request, the manager will evict tiles allocated to 38 // other clients. 39 void RequestTiles(size_t new_num_of_tiles, Key key); 40 41 Key PushBack(GlobalTileManagerClient* client); 42 43 // |key| must be already in manager. Move the tile manager client 44 // corresponding to |key| to most recent. This function should be called after 45 // RequestTiles. 46 void DidUse(Key key); 47 48 void Remove(Key key); 49 50 private: 51 friend struct base::DefaultLazyInstanceTraits<GlobalTileManager>; 52 GlobalTileManager(); 53 ~GlobalTileManager(); 54 55 // Continues evicting the inactive views until freeing up at least amount of 56 // tiles specified by |desired_num_tiles| to draw a view specified by |key|, 57 // or until all inactive views have been evicted. Returns the amount of 58 // memory that was actually evicted. This function is called when a 59 // request cannot be satisfied. 60 size_t Evict(size_t desired_num_tiles, Key key); 61 62 // Check that the sum of all client's tiles is equal to 63 // total_allocated_tiles_. 64 bool IsConsistent() const; 65 66 size_t num_tiles_limit_; 67 68 size_t total_allocated_tiles_; 69 ListType mru_list_; 70 base::SequenceChecker sequence_checker_; 71 72 DISALLOW_COPY_AND_ASSIGN(GlobalTileManager); 73 }; 74 75 } // namespace android_webview 76 77 #endif // ANDROID_WEBVIEW_BROWSER_GLOBAL_TILE_MANAGER_H_ 78