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Rendering Benchmarks (aka Smoothness benchmarks)

## Deprecated: see

Contact: nduca, ernstm**

We use the following terminology:

To run the rendering benchmarks you need:

Once you've got these things, you're ready to go. To run our top 25 page set

through our smoothness measurement (which tests scrolling speed for sites that scroll, or interaction speed for sites that have interactions):

./run_benchmark --browser=canary smoothness.top_25

To measure impl-side painting on important mobile sites:

tools/perf/run_benchmark --browser=canary smoothness.key_mobile_sites

To measure the key mobile sites on an attached android device:

tools/perf/run_benchmark --browser=android-chrome smoothness.top_25

To run the smoothness measurement on a Chrome OS device with IP address $CHROMEBOOK_IP from a host machine with a chromium checkout, do this:

tools/perf/run_benchmark --browser=cros-chromeos --remote=$CHROMEBOOK_IP smoothness.top_25

Lets break down this command a bit:

When you run a benchmark, you'll get some output that looks like this:

Pages: []

*RESULT frame_times: frame_times= [16.900000,17.280000,17.340000,16.810000,17.400000,17.500000,17.020000,16.820000,17.070000,17.190000,17.560000,17.670000,17.450000,17.570000,17.270000,17.410000,17.590000,17.530000,17.240000,17.550000,17.190000,17.140000,17.090000,17.500000,17.540000,17.000000,17.300000,17.600000,17.430000,17.070000,17.070000,17.760000,17.090000,16.950000,17.020000,17.040000,16.780000,17.060000,17.700000,17.850000,17.230000,17.090000,17.110000,17.110000,17.610000,17.200000,16.990000,17.180000,17.140000,17.130000,17.430000,17.080000,17.100000,17.100000,17.970000,17.150000,17.600000,17.400000,17.140000,16.920000,17.790000,16.780000,17.440000,16.860000,17.720000,17.700000,17.610000,16.940000,17.200000,16.980000,17.260000,17.310000,17.380000,16.960000,17.000000,17.500000,17.240000,17.170000] ms Avg frame_times: 17.267564ms Sd frame_times: 0.279332ms *RESULT jank: jank= 19.4673 *RESULT mean_frame_time: mean_frame_time= 17.268 ms *RESULT mostly_smooth: mostly_smooth= 1.0 RESULT telemetry_page_measurement_results: num_failed= 0 count RESULT telemetry_page_measurement_results: num_errored= 0 count

These are some key statistics for that page as it scrolled, in the default mode for that platform. But, lets say you wanted to run chrome with some extra commandline arguments. For this, --extra-browser-args is your friend:

tools/perf/run_benchmark --browser=canary smoothness.top_25 tools/perf/page_sets/top_25.json --extra-browser-args="--force-llamas-to-have-parachutes --use-rainbows-instad-of-omnibox"

Fun! Remember, unless you pass --disable-gpu-vsync, scrolling goes only as fast as your screen. So, for screen with 60 Hz refresh, 16.6 is usually a good thing.

Smoothness Metrics

These are the most important smoothness metrics:

Rasterize_And_Record Metrics

Throughout the metrics, you will see the words paint, record, and raster. These have very precise meanings:

In some sense impl-side painting splits paint into raster + record.

rasterize_and_record measurement calculates the time spent in raster and record. It automatically enables impl-side painting and only works on platforms that support this feature.

How it works

Telemetry performance testing framework

Page scrolling is done by telemetry's "scroll" action, tools/telemetry/telemetry/internal/actions/ On chrome, it boots the browser with --enable-gpu-benchmarking-extension, which exposes a beginSmoothScrollBy(numPixels, function() { callback }) API to javascript that simulates scrolling as would be done by the user. We then use it to move a page down.

Other synthetic gestures, such as pinch-to-zoom or swipe, are available. See the Synthetic Gestures in Chrome document for a full list of gestures and how they're implemented in Chrome.

The smoothness measurement tools/perf/measurements/ captures a trace from this interaction, and extracts the time stamps of frames that were generated. Specifically, the BenchmarkInstrumentation::ImplThreadRenderingStats and BenchmarkInstrumentation::MainThreadRenderingStats events are analyzed. These events are issued from cc/debug/ based on data collected through cc/debug/rendering_stats_instrumentation.h. The smoothness metric tools/perf/metrics/ is then used to calculate the metrics described above (mean_fram_time, jank, etc.).

Telemetry provides a way to separate out the measurement process from the interaction process from the actual pages being tested. We then maintain a number of important lists of web pages (page sets), some synthetic some real, in tools/perf/page_sets, grouped by their kind of importance. top_25, key_desktop_sites and key_mobile_sites are likely of particular interest to users.

Telemetry provides a mechanism to very reliably record a web page and then replay it many times in that exact recorded state. We (Chrome team) cannot make our recordings public since the assets the recording are the property of the site owners. However, we have exposed a utility that anyone can use to make their own recordings:

tools/perf/record_wpr --browser=system tools/perf/page_sets/top_25.json

This will place a file called top_25.wpr in tools/perf/page_sets/data that is an archive of the data required to replay those pages back over-and-over again without deviation.

Adding credentials to test live sites that require a logged in user

As part of GPU testing, we often want to measure the performance of a site like Gmail, or Facebook, that sit behind a login. We do not give out logins for these, but if you have your own, you can put a credentials.json in tools/perf/page_sets/data or ~/.telemetry-credentials in the style of tools/telemetry/examples/credentials_example.json with the right logins and telemetry will automatically then login to gmail or facebook for you. Patches are welcome to add support for other sites as well.