cc mojo: Use ArrayDataViews in RenderPasses
This CL makes use of the newly introduced Array DataViews
in cc StructTraits in order to improve serialization (and
to a lesser degree deserialization) performance.
This CL improves serialization performance by an average of
18% on an HP Z620. Deserialization performance improves
between 7 to 10%.
Prior to the ability to inspect Array and Struct DataViews
in parent StructTraits, we had to do extra work at
serialization time in order to capture state that spans
individual structs within a larger struct.
This CL addresses two of those cases:
1. Previously, QuadList maintained an extra array of
materials. This array existed so that we could preallocate
the appropriately typed DrawQuads during deserialization.
StructTraits assume a preallocated type and populated
fields in that type.
Alternatively we could have deserialized DrawQuads into
unique_ptrs, but cc required that we allocate DrawQuads
inline within a buffer in order to minimize the cost of
allocations (there can be hundreds of DrawQuads in a
CompositorFrame).
2. Previously, SharedQuadStates were serialized
independently of DrawQuads. However, in in-memory form,
DrawQuads refer to SharedQuadStates via raw pointers. In
order to allow DrawQuads and SharedQuadStates to deserialize
independently, as was required previously by StructTraits, a third
array was serialized "shared_quad_state_references" which was equal in
size to the QuadList. Each slot corresponded to an index in
the SharedQuadStateList. After the QuadList and SharedQuadStateList were
serialized, shared_quad_state_references updated the raw
pointers in the DrawQuads in the quad list to refer to the
SharedQuadStates. This required revisiting all deserialized
DrawQuads again.
In both 1. and 2. additional state needed to be allocated on the heap
during serialization. In pprof profiling, it became apparent that much
of the cost of serialization was in SetupContext. This CL eliminates
that cost.
Performance measures are available here:
https://docs.google.com/a/google.com/spreadsheets/d/13Y0I-BVDrQC4RHIzMSs0vl0QPe8xFAhYMUAXaxoEqgg/pubhtml
BUG=624459
TBR=danakj@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
Review-Url: https://codereview.chromium.org/2174843003
Cr-Commit-Position: refs/heads/master@{#408809}
CrOS-Libchrome-Original-Commit: edd40fdc29170e97ab54578fdc5096fc564c0ccb
3 files changed