cc: Keep most recently used resources at the front of resource queue.

cc/resources/resource_pool.cc

Index: cc/resources/resource_pool.cc
diff --git a/cc/resources/resource_pool.cc b/cc/resources/resource_pool.cc
index 835c37d6c32d9f23029bcfea419ad6f8f2b3f2fc..227fecf43b1ca51bf07a053094a17171ef909b15 100644
--- a/cc/resources/resource_pool.cc
+++ b/cc/resources/resource_pool.cc
@@ -91,8 +91,12 @@ ResourcePool::~ResourcePool() {
 
 Resource* ResourcePool::AcquireResource(const gfx::Size& size,
                                         ResourceFormat format) {
-  for (ResourceDeque::iterator it = unused_resources_.begin();
-       it != unused_resources_.end(); ++it) {
+  // Traverse the |unused_resources_| from rear end as MRU resources are
+  // held at the rear end of the queue. This touches LRU resources only if
+  // needed, which inreases possibility of expiring more LRU resources
+  // within kResourceExpirationDelayMs.
+  for (ResourceDeque::reverse_iterator it = unused_resources_.rbegin();
+       it != unused_resources_.rend(); ++it) {
     ScopedResource* resource = *it;
     DCHECK(resource_provider_->CanLockForWrite(resource->id()));
 
@@ -102,7 +106,7 @@ Resource* ResourcePool::AcquireResource(const gfx::Size& size,
       continue;
 
     // Transfer resource to |in_use_resources_|.
-    in_use_resources_.set(resource->id(), unused_resources_.take(it));
+    in_use_resources_.set(resource->id(), unused_resources_.rtake(it));
     in_use_memory_usage_bytes_ += ResourceUtil::UncheckedSizeInBytes<size_t>(
         resource->size(), resource->format());
     return resource;
@@ -130,18 +134,22 @@ Resource* ResourcePool::AcquireResource(const gfx::Size& size,
 Resource* ResourcePool::TryAcquireResourceWithContentId(uint64_t content_id) {

[reveman, 2015/11/02 01:47:07]

It shouldn't matter in what order we search the resources when looking for a
specific content id. Can we leave this function unmodified?

[prashant.n, 2015/11/02 04:07:20]

Ahh! I missed one content id = one resource (next_tile_id_). May be in this
patch it will not be needed. When we move the code to common function, there we
need to change this function.

   DCHECK(content_id);
 
-  auto it = std::find_if(unused_resources_.begin(), unused_resources_.end(),
-                         [content_id](const PoolResource* pool_resource) {
-                           return pool_resource->content_id() == content_id;
-                         });
-  if (it == unused_resources_.end())
+  // TODO(prashant.n): Move resource finding logic to common function.

[reveman, 2015/11/02 01:47:07]

I don't see much duplication of resource finding logic. Is this worthwhile?

[prashant.n, 2015/11/02 04:07:20]

Yes most of the code in getting resource from unused resources from
AcquireResource and TryAcquireResourceWithContentId is same execpt the search
criteria.

I think we should have separate function to do that job, which I was thining to
put in separate patch.

[reveman, 2015/11/02 04:32:59]

Ok, feel free to put up a patch for that and I'll review it. No need for this
TODO.

+  ResourceDeque::reverse_iterator it = unused_resources_.rbegin();
+  for (; it != unused_resources_.rend(); ++it) {
+    PoolResource* pool_resource = *it;
+    if (pool_resource->content_id() != content_id)
+      continue;
+  }
+
+  if (it == unused_resources_.rend())
     return nullptr;
 
   Resource* resource = *it;
   DCHECK(resource_provider_->CanLockForWrite(resource->id()));
 
   // Transfer resource to |in_use_resources_|.
-  in_use_resources_.set(resource->id(), unused_resources_.take(it));
+  in_use_resources_.set(resource->id(), unused_resources_.rtake(it));
   in_use_memory_usage_bytes_ += ResourceUtil::UncheckedSizeInBytes<size_t>(
       resource->size(), resource->format());
   return resource;