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Commit 336f3b37 authored by Arun's avatar Arun Committed by Arne Coucheron
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Reduce hwui CPU time by using glDrawRangeElements 

The CPU overhead of glDrawElements in the GPU driver is significant
with client-side vertex data (unique per draw call) as the driver has
to calculate the mininimum and maximum indices from the index buffer
in order to evaluate the range of vertex data required. This can be
avoided by keeping track of the min-max in hwui and passing it with
glDrawRangeElements. This requires OpenGL ES3.0 support (which is
already checked for elsewhere in hwui).

Test: manual - visual inspection on fugu (nexus player)

Change-Id: I57bb1ddd239a1032f74f1cd2683bbe0970e84bd9
parent 6334326c

libs/hwui/Glop.h

+1 −0
Original line number Diff line number Diff line
@@ -112,6 +112,7 @@ public: 
        } vertices;



        int elementCount;

        int vertexCount; // only used for meshes (for glDrawRangeElements)

        TextureVertex mappedVertices[4];

    } mesh;

libs/hwui/GlopBuilder.cpp

+1 −0
Original line number Diff line number Diff line
@@ -210,6 +210,7 @@ GlopBuilder& GlopBuilder::setMeshVertexBuffer(const VertexBuffer& vertexBuffer) 
            alphaVertex ? kAlphaVertexStride : kVertexStride };

    mOutGlop->mesh.elementCount = indices

                ? vertexBuffer.getIndexCount() : vertexBuffer.getVertexCount();

    mOutGlop->mesh.vertexCount = vertexBuffer.getVertexCount(); // used for glDrawRangeElements()

    return *this;

}

libs/hwui/renderstate/RenderState.cpp

+13 −3
Original line number Diff line number Diff line
@@ -370,18 +370,28 @@ void RenderState::render(const Glop& glop, const Matrix4& orthoMatrix) { 
        const GLbyte* vertexData = static_cast<const GLbyte*>(vertices.position);

        while (elementsCount > 0) {

            GLsizei drawCount = std::min(elementsCount, (GLsizei) kMaxNumberOfQuads * 6);

            GLsizei vertexCount = (drawCount / 6) * 4;

            meshState().bindPositionVertexPointer(vertexData, vertices.stride);

            if (vertices.attribFlags & VertexAttribFlags::TextureCoord) {

                meshState().bindTexCoordsVertexPointer(

                        vertexData + kMeshTextureOffset, vertices.stride);

            }



            if (mCaches->extensions().getMajorGlVersion() >= 3) {

                glDrawRangeElements(mesh.primitiveMode, 0, vertexCount-1, drawCount, GL_UNSIGNED_SHORT, nullptr);

            } else {

                glDrawElements(mesh.primitiveMode, drawCount, GL_UNSIGNED_SHORT, nullptr);

            }

            elementsCount -= drawCount;

            vertexData += (drawCount / 6) * 4 * vertices.stride;

            vertexData += vertexCount * vertices.stride;

        }

    } else if (indices.bufferObject || indices.indices) {

        if (mCaches->extensions().getMajorGlVersion() >= 3) {

            // use glDrawRangeElements to reduce CPU overhead (otherwise the driver has to determine the min/max index values)

            glDrawRangeElements(mesh.primitiveMode, 0, mesh.vertexCount-1, mesh.elementCount, GL_UNSIGNED_SHORT, indices.indices);

        } else {

            glDrawElements(mesh.primitiveMode, mesh.elementCount, GL_UNSIGNED_SHORT, indices.indices);

        }

    } else {

        glDrawArrays(mesh.primitiveMode, 0, mesh.elementCount);

    }