cc: Add command line switch to control resource usage for impl-side painting.

cc/resources/resource_pool.cc

 // Copyright 2012 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 "cc/resources/resource_pool.h"
 
 #include "cc/resources/resource_provider.h"
 
 namespace cc {
 
@@ skipping 12 matching lines @@
 
 ResourcePool::Resource::~Resource() {
   DCHECK(id());
   DCHECK(resource_provider_);
   resource_provider_->DeleteResource(id());
 }
 
 ResourcePool::ResourcePool(ResourceProvider* resource_provider)
     : resource_provider_(resource_provider),
       max_memory_usage_bytes_(0),
-      memory_usage_bytes_(0) {
+      max_unused_memory_usage_bytes_(0),
+      memory_usage_bytes_(0),
+      unused_memory_usage_bytes_(0) {
 }
 
 ResourcePool::~ResourcePool() {
-  SetMaxMemoryUsageBytes(0);
+  SetMaxMemoryUsageBytes(0, 0);
 }
 
 scoped_ptr<ResourcePool::Resource> ResourcePool::AcquireResource(
     const gfx::Size& size, GLenum format) {
   for (ResourceList::iterator it = resources_.begin();
        it != resources_.end(); ++it) {
     Resource* resource = *it;
 
     // TODO(epenner): It would be nice to DCHECK that this
     // doesn't happen two frames in a row for any resource
     // in this pool.
     if (!resource_provider_->CanLockForWrite(resource->id()))
       continue;
 
     if (resource->size() != size)
       continue;
     if (resource->format() != format)
       continue;
 
     resources_.erase(it);
+    unused_memory_usage_bytes_ -= resource->bytes();
     return make_scoped_ptr(resource);
   }
 
   // Create new resource.
   Resource* resource = new Resource(
       resource_provider_, size, format);
 
   // Extend all read locks on all resources until the resource is
   // finished being used, such that we know when resources are
   // truly safe to recycle.
   resource_provider_->EnableReadLockFences(resource->id(), true);
 
   memory_usage_bytes_ += resource->bytes();
   return make_scoped_ptr(resource);
 }
 
 void ResourcePool::ReleaseResource(
     scoped_ptr<ResourcePool::Resource> resource) {
-  if (memory_usage_bytes_ > max_memory_usage_bytes_) {
+  if (MemoryUsageTooHigh()) {
     memory_usage_bytes_ -= resource->bytes();
     return;
   }
 
+  unused_memory_usage_bytes_ += resource->bytes();
   resources_.push_back(resource.release());
 }
 
-void ResourcePool::SetMaxMemoryUsageBytes(size_t max_memory_usage_bytes) {
+void ResourcePool::SetMaxMemoryUsageBytes(
+    size_t max_memory_usage_bytes,
+    size_t max_unused_memory_usage_bytes) {
   max_memory_usage_bytes_ = max_memory_usage_bytes;
+  max_unused_memory_usage_bytes_ = max_unused_memory_usage_bytes;
 
   while (!resources_.empty()) {
-    if (memory_usage_bytes_ <= max_memory_usage_bytes_)
+    if (!MemoryUsageTooHigh())
       break;
-    Resource* resource = resources_.front();
-    resources_.pop_front();
+
+    // MRU eviction pattern as least recently used is less likely to
+    // be blocked by read lock fence.
+    Resource* resource = resources_.back();
+    resources_.pop_back();
     memory_usage_bytes_ -= resource->bytes();
+    unused_memory_usage_bytes_ -= resource->bytes();
     delete resource;
   }
 }
 
+bool ResourcePool::MemoryUsageTooHigh() {
+  if (memory_usage_bytes_ > max_memory_usage_bytes_)
+    return true;
+  if (unused_memory_usage_bytes_ > max_unused_memory_usage_bytes_)
+    return true;
+  return false;
+}
+
 }  // namespace cc