Global GPU memory manager for android webview

android_webview/browser/global_tile_manager.cc

+// 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.
+
+#include "android_webview/browser/global_tile_manager.h"
+#include "android_webview/browser/global_tile_manager_client.h"
+#include "base/lazy_instance.h"
+
+namespace android_webview {
+
+namespace {
+base::LazyInstance<GlobalTileManager>::Leaky g_tile_manager =
+    LAZY_INSTANCE_INITIALIZER;
+// The soft limit of the number of file descriptors per process is 1024 on
+// Android and gralloc buffers may not be the only thing that uses file
+// descriptors. For each tile, there is a gralloc buffer backing it, which
+// uses 2 FDs.
+const size_t kNumTilesLimit = 450;
+
+}  // namespace
+
+// static
+GlobalTileManager* GlobalTileManager::GetInstance() {
+  return g_tile_manager.Pointer();
+}
+
+void GlobalTileManager::Remove(Key key) {
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  DCHECK(mru_list_.end() != key);
+
+  total_allocated_tiles_ -= (*key)->GetNumTiles();
+  mru_list_.erase(key);
+  DCHECK(IsConsistent());
+}
+
+size_t GlobalTileManager::Evict(size_t desired_num_tiles, Key key) {
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  size_t total_evicted_tiles = 0;
+
+  // Evicts from the least recent drawn view, until the disired number of tiles
+  // can be reclaimed, or until we've evicted all inactive views.
+  ListType::reverse_iterator it;
+  for (it = mru_list_.rbegin(); it != mru_list_.rend(); it++) {
+    // key represents the view that requested the eviction, so we don't need to
+    // evict the requester itself. And we only evict the inactive views,
+    // which are all the views after the requester.
+    if (*it == *key)
+      break;
+
+    size_t evicted_tiles = (*it)->GetNumTiles();
+    (*it)->SetNumTiles(0, true);
+
+    total_evicted_tiles += evicted_tiles;
+    if (total_evicted_tiles >= desired_num_tiles)
+      break;
+  }
+
+  return total_evicted_tiles;
+}
+
+void GlobalTileManager::RequestTiles(size_t new_num_of_tiles, Key key) {
+  DCHECK(IsConsistent());
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  size_t old_num_of_tiles = (*key)->GetNumTiles();
+  size_t num_of_active_views = std::distance(mru_list_.begin(), key) + 1;
+  size_t tiles_per_view_limit;
+  if (num_of_active_views == 0)
+    tiles_per_view_limit = kNumTilesLimit;
+  else
+    tiles_per_view_limit = kNumTilesLimit / num_of_active_views;
+  new_num_of_tiles = std::min(new_num_of_tiles, tiles_per_view_limit);
+  size_t new_total_allocated_tiles =
+      total_allocated_tiles_ - old_num_of_tiles + new_num_of_tiles;
+  // Has enough tiles to satisfy the request.
+  if (new_total_allocated_tiles <= kNumTilesLimit) {
+    total_allocated_tiles_ = new_total_allocated_tiles;
+    (*key)->SetNumTiles(new_num_of_tiles, false);
+    return;
+  }
+
+  // Does not have enough tiles. Now evict other clients' tiles.
+  size_t tiles_left = kNumTilesLimit - total_allocated_tiles_;
+
+  size_t evicted_tiles = Evict(new_total_allocated_tiles - kNumTilesLimit, key);
+  if (evicted_tiles >= new_total_allocated_tiles - kNumTilesLimit) {
+    new_total_allocated_tiles -= evicted_tiles;
+    total_allocated_tiles_ = new_total_allocated_tiles;
+    (*key)->SetNumTiles(new_num_of_tiles, false);
+    return;
+  } else {
+    total_allocated_tiles_ = kNumTilesLimit;
+    (*key)->SetNumTiles(tiles_left + old_num_of_tiles + evicted_tiles, false);
+    return;
+  }
+}
+
+GlobalTileManager::Key GlobalTileManager::PushBack(
+    GlobalTileManagerClient* client) {
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  DCHECK(mru_list_.end() ==
+         std::find(mru_list_.begin(), mru_list_.end(), client));
+  mru_list_.push_back(client);
+  Key back = mru_list_.end();
+  back--;
+  return back;
+}
+
+void GlobalTileManager::DidUse(Key key) {
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  DCHECK(mru_list_.end() != key);
+
+  mru_list_.splice(mru_list_.begin(), mru_list_, key);
+}
+
+GlobalTileManager::GlobalTileManager() {
+  total_allocated_tiles_ = 0;
+}
+
+GlobalTileManager::~GlobalTileManager() {
+}
+
+bool GlobalTileManager::IsConsistent() const {
+  size_t total_tiles = 0;
+  ListType::const_iterator it;
+  for (it = mru_list_.begin(); it != mru_list_.end(); it++) {
+    total_tiles += (*it)->GetNumTiles();
+  }
+
+  bool is_consistent =
+      (total_tiles <= kNumTilesLimit && total_tiles == total_allocated_tiles_);
+
+  return is_consistent;
+}
+
+}  // namespace webview