cc::ResourcePool - Re-use larger resources for smaller requests

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 c2003758c4ba65ef0348e1988699c79f41dfb1b6..ddef9402ca2917bffb08e6ca1df46d572e100848 100644
--- a/cc/resources/resource_pool.cc
+++ b/cc/resources/resource_pool.cc
@@ -24,8 +24,31 @@ using base::trace_event::MemoryAllocatorDump;
 using base::trace_event::MemoryDumpLevelOfDetail;
 
 namespace cc {
+namespace {
+bool ResourceMeetsSizeRequirements(const gfx::Size& requested_size,
+                                   const gfx::Size& actual_size) {
+  const float kReuseThreshold = 2.0f;
+
+  // Allocating new resources is expensive, and we'd like to re-use our
+  // existing ones within reason. Allow a larger resource to be used for a
+  // smaller request.
+  if (actual_size.width() < requested_size.width() ||
+      actual_size.height() < requested_size.height())
+    return false;
+  // But don't use a resource that is more than |kReuseThreshold| times the
+  // requested pixel area, as we want to free unnecessarily large resources.
+  float actual_area = actual_size.GetArea();

[danakj, 2017/03/10 18:55:40]

This will crash if it overflows (GetArea uses safe math). But sizes here can't
be a problem for that right?

[ericrk, 2017/03/10 20:04:07]

I'm assuming that this can't be a problem - the sizes in use are all tile sizes,
capped at max_texture_size. Added a comment.

+  float requested_area = requested_size.GetArea();
+  if (actual_area / requested_area > kReuseThreshold)
+    return false;
+
+  return true;
+}
+
+}  // namespace
+
 base::TimeDelta ResourcePool::kDefaultExpirationDelay =
-    base::TimeDelta::FromSeconds(1);
+    base::TimeDelta::FromSeconds(5);
 
 void ResourcePool::PoolResource::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd,
@@ -119,7 +142,7 @@ Resource* ResourcePool::ReuseResource(const gfx::Size& size,
 
     if (resource->format() != format)
       continue;
-    if (resource->size() != size)
+    if (!ResourceMeetsSizeRequirements(size, resource->size()))
       continue;
     if (resource->color_space() != color_space)
       continue;