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drawElements Quality Program Test Specification
Copyright 2014 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.
Performance tests
This test specification describes general techniques and methodologies used
in performance test cases.
Measuring performance:
Performance test cases must satisfy following conditions:
+ Result should represent the performance of the tested feature or use case.
- Use of any other features should be kept at minimum.
- Architecture-specific optimizations should not affect result unless they
target the feature being tested.
- Measurement overhead should be minimized.
+ Hardware must be utilized to the maximum.
- In most cases total throughput is more important than latency.
- Latency is measured where it matters.
- Test cases should behave like other graphics-intensive applications on
that platform. This usually means that test cases should render multiple
frames and utilize platform-defined standard mechanisms to display each
frame on screen.
+ Test result should be stable across test runs.
- Final result should be a function of results from multiple iterations if
performance is expected to vary between iterations (due to undeterministic
scheduling for example).
- Simple average may not always be the right function, often stability of
the performance is more important from user experience perspective.
+ Test result values should be meaningful.
- Result should be meaningful without knowing the exact implementation
details of the test case.
- Good example: Millions of pixels or vertices with shader X per second
- Bad example: Frames per second
+ Results can be compared across different implementations and configurations.
- If possible, configuration changes (viewport size for example) should not
affect the test result.
- Where configuration may affect the result, test log should include the
configuration details.
Test output:
Test cases will log at least following variables, if available:
* Viewport size
* Color, depth, stencil and multisample bits
* Number of draw calls
* Shader program source
* Automatic calibration values
* Individual iteration times (if iteration count is reasonable)
* Minimum and maximum iteration times
* Average iteration time
* Minimum and maximum computed performance
* Average computed performance
Shader execution tests:
Shader execution tests measure the performance of single pair of vertex and
fragment shaders, optionally combined with fixed-function per-fragment
operations such as blending.
Each iteration (frame) renders N grids of quads. Each grid, drawn with single
draw call, fills the screen entirely without any overlap between quads.
The number of quads depends on targeted vertex load. Test cases targeting
fragment shaders only use a single quad. N (number of times screen is filled)
is chosen either automatically to target certain iteration time or specified
by the test case explicitly.
Test cases that measure fragment-side performance must make sure fragments
are not discarded early due to Z-culling or any other optimization. The
preferred way to do this is to enable simple additive blending. The extra
cost of that is one read from the framebuffer and per-channel saturating
The result is MPix/s, MVert/s or weighted sum of both depending on test
case type.