cc: Partial tile update for one-copy raster.

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 22847809ba3c196f66df1112d978d56342665b3a..029958dffdba3e0ba662b923f43b8d793424a7c9 100644
--- a/cc/resources/resource_pool.cc
+++ b/cc/resources/resource_pool.cc
@@ -21,7 +21,8 @@ ResourcePool::ResourcePool(ResourceProvider* resource_provider, GLenum target)
 
 ResourcePool::~ResourcePool() {
   while (!busy_resources_.empty()) {
-    DidFinishUsingResource(busy_resources_.front());
+    auto const& front = busy_resources_.front();
+    DidFinishUsingResource(front.resource, front.id);
     busy_resources_.pop_front();
   }
 
@@ -37,7 +38,7 @@ scoped_ptr<ScopedResource> ResourcePool::AcquireResource(
   for (ResourceList::iterator it = unused_resources_.begin();
        it != unused_resources_.end();
        ++it) {
-    ScopedResource* resource = *it;
+    ScopedResource* resource = it->resource;
     DCHECK(resource_provider_->CanLockForWrite(resource->id()));
 
     if (resource->format() != format)
@@ -59,8 +60,51 @@ scoped_ptr<ScopedResource> ResourcePool::AcquireResource(
   return resource.Pass();
 }
 
-void ResourcePool::ReleaseResource(scoped_ptr<ScopedResource> resource) {
-  busy_resources_.push_back(resource.release());
+scoped_ptr<ScopedResource> ResourcePool::TryAcquireOldResource(
+    const gfx::Size& size,
+    ResourceFormat format,
+    uint64_t id) {
+  if (!id)
+    return nullptr;
+
+  auto it = std::find_if(unused_resources_.begin(), unused_resources_.end(),
+                         [id](const PoolResource& pr) { return pr.id == id; });
+  if (it == unused_resources_.end())
+    return nullptr;
+
+  ScopedResource* resource = it->resource;
+  DCHECK(resource_provider_->CanLockForWrite(resource->id()));
+  if (resource->format() != format || resource->size() != size)
+    return nullptr;
+
+  unused_resources_.erase(it);
+  unused_memory_usage_bytes_ -= resource->bytes();
+  return make_scoped_ptr(resource);
+}
+
+scoped_ptr<ScopedResource> ResourcePool::TryAcquireOldBusyResource(

[danakj, 2015/05/15 03:19:34]

I was thinking about it and I think this reusing busy resources is too sketchy
and not worth it.

We're returning the resource in here as a scoped_ptr but it still should be in
the busy_resources list, cuz it is busy. Else we need to track its unbusy state
somehow when we return it. It seems fragile.

Also, it's only needed for a cornercase of an invalidation in the prepaint area.
For UI compositor there's basically no prepaint issue. And for animations in
prepaint, we try to avoid that in blink (disabling animated gifs etc).

I'm going to remove the busy resource part from this patch, which also removes
all the complicated copying code and having 2 resources in the OneCopy worker
pool code.

[piman, 2015/05/15 03:38:35]

It sounds ok for UI, but for the renderer, aren't resources sent to the parent
always busy (i.e. TryAcquireOldResource will always fail)?
We can leave it out of this patch, but I think it'd be nice to hit later / as a
followup. E.g. do we have to return it as a scoped_ptr? We're only reading from
it. I guess we need to make sure it's not evicted nor written to if referenced
by a task for reading.

+    const gfx::Size& size,
+    ResourceFormat format,
+    uint64_t id) {
+  if (!id)
+    return nullptr;
+
+  auto it = std::find_if(busy_resources_.begin(), busy_resources_.end(),
+                         [id](const PoolResource& pr) { return pr.id == id; });
+  if (it == busy_resources_.end())
+    return nullptr;
+
+  ScopedResource* resource = it->resource;
+  DCHECK(resource_provider_->CanLockForWrite(resource->id()));
+  if (resource->format() != format || resource->size() != size)
+    return nullptr;
+
+  return make_scoped_ptr(resource);
+}
+
+void ResourcePool::ReleaseResource(scoped_ptr<ScopedResource> resource,
+                                   uint64_t id) {
+  busy_resources_.push_back(PoolResource(resource.release(), id));
 }
 
 void ResourcePool::SetResourceUsageLimits(size_t max_memory_usage_bytes,
@@ -85,7 +129,7 @@ void ResourcePool::ReduceResourceUsage() {
     // can't be locked for write might also not be truly free-able.
     // We can free the resource here but it doesn't mean that the
     // memory is necessarily returned to the OS.
-    ScopedResource* resource = unused_resources_.front();
+    ScopedResource* resource = unused_resources_.front().resource;
     unused_resources_.pop_front();
     memory_usage_bytes_ -= resource->bytes();
     unused_memory_usage_bytes_ -= resource->bytes();
@@ -108,13 +152,13 @@ void ResourcePool::CheckBusyResources(bool wait_if_needed) {
   ResourceList::iterator it = busy_resources_.begin();
 
   while (it != busy_resources_.end()) {
-    ScopedResource* resource = *it;
+    ScopedResource* resource = it->resource;
 
     if (wait_if_needed)
       resource_provider_->WaitReadLockIfNeeded(resource->id());
 
     if (resource_provider_->CanLockForWrite(resource->id())) {
-      DidFinishUsingResource(resource);
+      DidFinishUsingResource(resource, it->id);
       it = busy_resources_.erase(it);
     } else {
       ++it;
@@ -122,9 +166,10 @@ void ResourcePool::CheckBusyResources(bool wait_if_needed) {
   }
 }
 
-void ResourcePool::DidFinishUsingResource(ScopedResource* resource) {
+void ResourcePool::DidFinishUsingResource(ScopedResource* resource,
+                                          uint64_t id) {
   unused_memory_usage_bytes_ += resource->bytes();
-  unused_resources_.push_back(resource);
+  unused_resources_.push_back(PoolResource(resource, id));
 }
 
 }  // namespace cc