android_webview/browser/global_tile_manager.h

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