ANGLE Restricted Traces

July 1, 2026 ยท View on GitHub

The files in this directory are traces of real applications. We host them internally because they may contain third party IP which we don't want to share publicly.

Accessing the traces

In order to compile and run with these, you must be granted access by Google, then authenticate with CIPD. Googlers, use your @google account.

cipd auth-login

Add the following to ANGLE's .gclient file:

    "custom_vars": {
      "checkout_angle_restricted_traces": True
    },

Note: alternatively, you can checkout only a few specific traces using the following format (angle_restricted_traces in gn args below should be a matching list or a subset):

    "custom_vars": {
      "checkout_angle_restricted_trace_{trace_name_1}": True,
      "checkout_angle_restricted_trace_{trace_name_2}": True,
      ...
    },

Then use gclient to pull down binary files from CIPD.

gclient sync -D

This should result in a number of directories created in src/tests/restricted_traces that contain the trace files listed in restricted_traces.json:

$ ls -d src/tests/restricted_traces/*/
src/tests/restricted_traces/aliexpress/
src/tests/restricted_traces/angry_birds_2_1500/
src/tests/restricted_traces/arena_of_valor/
src/tests/restricted_traces/asphalt_8/
src/tests/restricted_traces/brawl_stars/
src/tests/restricted_traces/bus_simulator_indonesia/
src/tests/restricted_traces/candy_crush_500/
src/tests/restricted_traces/clash_of_clans/
src/tests/restricted_traces/clash_royale/
src/tests/restricted_traces/cod_mobile/
...

Building the trace tests

To build for Android, follow the steps in DevSetupAndroid.md (Recommend using the Performance arguments for best performance)

To build for Desktop, follow the steps in DevSetup.md

When that is working, add the following GN arg to your setup:

build_angle_trace_perf_tests = true

Selecting which traces to build

Since the traces are numerous, you should limit compilation to a subset with the following GN arg:

angle_restricted_traces = ["among_us 5", "street_fighter_duel 1"]

If you choose not to pick any traces and build them all, you must follow different steps for Android. Skip ahead to Building and running all traces for Android

To build the trace tests:

autoninja -C out/<config> angle_trace_tests

Running the trace tests

The trace tests can be run with default options like so:

out/<config>/angle_trace_tests

To select a specific trace to run, provide it with a filter:

out/<config>/angle_trace_tests --gtest_filter=TraceTest.<trace_name>

The specific options available with traces can be found in the PerfTests README

Common options used are:

# Use ANGLE as the driver with the system's Vulkan driver as backend
--use-angle=vulkan

# Use the system's native GLES driver
--use-gl=native

Building and running all traces for Android

Our trace library has gotten large enough that they no longer fit in a single APK. To support building and running the entire library, we can compile the libraries by themselves, outside of the APK, and push them to locations accessible by the test harness.

To do so, remove angle_restricted_traces from your GN args, then compile with:

autoninja -C out/<config> angle_trace_perf_tests

and run with (including recommended options):

out/<config>/angle_trace_tests --filter='*among_us*' --verbose --fixed-test-time-with-warmup 10

If more than one device is connected, the target device serial should be provided as well:

ANDROID_SERIAL=<device_serial> out/<config>/angle_trace_tests ...

Capturing and adding new Android traces

Generally we want to use a Debug setup for recording new traces. That allows us to see asserts and errors if the tracer needs to be improved. Add the following GN arg to your Debug setup:

angle_with_capture_by_default = true

After building and installing the APK with the above arg, we're ready to start capturing.

If capturing a new trace using OpenCL, also add the following to your Debug setup:

angle_enable_cl = true
Example of full OpenCL GN arg Debug setup for Capture 
# Target information
is_clang = true
target_cpu = "arm64"
target_os = "android"

# Enable CL + backends
angle_enable_cl = true
angle_enable_vulkan = true

# Debug mode flags
is_debug = true
symbol_level = 2
strip_debug_info = false
android_full_debug = true
ignore_elf32_limitations = true

# Other flag settings
is_official_build = false
is_component_build = false
angle_extract_native_libs = true

Capturing long traces

The tracer will capture traces larger than the available physical memory on the target device. However, for very long traces there may be noticeable hitching during disk-writes once available memory is exhausted. If this becomes problematic a release build can be used, or to minimize hitching completely, disable binary data file compression. To do this ensure that the following property is set for capture:

adb shell setprop debug.angle.capture.compression 0

Determine the target app

We first need to identify which application we want to trace. That can generally be done by looking at the web-based Play Store entry for your app. For instance, Angry Birds 2 is listed here: https://play.google.com/store/apps/details?id=com.rovio.baba

If there is no Play Store entry for your app, there are a couple of ways you can determine the app's name.

If you have a userdebug build of Android, you can check logcat when you launch the application. You should see an entry like this:

GraphicsEnvironment: ANGLE Developer option for 'com.rovio.baba' set to: 'default'

If you just have an APK, you can use the following command to find the package name:

$ aapt dump badging angry_birds_2.apk | grep package
package: name='com.rovio.baba' versionCode='24900001' versionName='2.49.1' platformBuildVersionName=''

You can also just guess at the package name, then check your device to see if it is installed. Keep trying combinations until you find it:

$ adb shell pm list packages | grep rovio
package:com.rovio.baba

Track the package name for use in later steps:

export PACKAGE_NAME=com.rovio.baba

Choose a trace name

Next, we need to chose a name for the trace. Choose something simple that identifies the app, then use snake case. This will be the name of the trace files, including the trace directory. Changing this value later is possible, but not recommended.

export LABEL=angry_birds_2

Opt the application into ANGLE

Note: If running an executable, not an application/APK, these settings don't apply.

Next, opt the application into using your ANGLE with capture enabled by default:

adb shell settings put global angle_debug_package org.chromium.angle
adb shell settings put global angle_gl_driver_selection_pkgs $PACKAGE_NAME
adb shell settings put global angle_gl_driver_selection_values angle

Set up some Capture/Replay properties

We also need to set some debug properties used by the tracer.

Ensure frame capture is enabled. This might be redundant, but ensure the property isn't set to zero, which disables frame capture.

adb shell setprop debug.angle.capture.enabled 1

Empty the start and end frames. Again, this might be redundant, but it is less confusing.

adb shell setprop debug.angle.capture.frame_start '""'
adb shell setprop debug.angle.capture.frame_end '""'

Set the label to be used in the trace files

adb shell setprop debug.angle.capture.label $LABEL

Set a trigger value to be used by the tracer. This should be set to the number of frames you want to capture. We typically use 10 to get an idea of how a scene is running, but some workloads require more. Use your discretion here:

adb shell setprop debug.angle.capture.trigger 10

For OpenCL capture, a trigger most likely won't be wanted. So, set the frame_start and frame_end values accordingly. Each clEnqueueNDRangeKernel is considered the end of a frame.

adb shell setprop debug.angle.capture.frame_start 1
adb shell setprop debug.angle.capture.frame_end 100.

But if you do want to capture OpenCL and the end frame isn't clear, use the end_capture feature. See End the capture early for more information.

Create output location

We need to write out the trace file in a location accessible by the app. We use the app's data storage on sdcard, but create a subfolder to isolate ANGLE's files:

adb shell mkdir -p /sdcard/Android/data/$PACKAGE_NAME/angle_capture

If the [capture](#Trigger the capture) failed due to these errors:

Output directory
'/sdcard/Android/data/$PACKAGE_NAME/angle_capture/' does not exist.
Create it over adb using mkdir.

Could not open binary data file /sdcard/Android/data/$PACKAGE_NAME/angle_capture/$LABEL.angledata.gz

It means the app does not have access to /sdcard/. We will need to use the app's own data storage, which requires enabling adb root first:

adb root
adb shell setprop debug.angle.capture.out_dir /data/data/$PACKAGE_NAME/angle_capture
adb shell mkdir -p /data/data/$PACKAGE_NAME/angle_capture

Start the target app

From here, you can start the application. You should see logcat entries like the following, indicating that we've succesfully turned on capturing:

ANGLE   : INFO: Capture trigger detected, disabling capture start/end frame.
ANGLE   : INFO: Limiting binary format support count to zero while FrameCapture enabled
ANGLE   : INFO: Limiting image unit count to 8 while FrameCapture enabled
ANGLE   : INFO: Setting uniform buffer offset alignment to 256 while FrameCapture enabled
ANGLE   : INFO: Disabling GL_EXT_map_buffer_range and GL_OES_mapbuffer during capture, which are not supported on some native drivers
ANGLE   : INFO: Disabling GL_CHROMIUM_bind_uniform_location during capture, which is not supported on native drivers
ANGLE   : INFO: Disabling GL_NV_shader_noperspective_interpolation during capture, which is not supported on some native drivers
ANGLE   : INFO: Limiting draw buffer count to 4 while FrameCapture enabled

Trigger the capture

Note: If you have set the start and end frame, this step does not apply.

When you have reached the content in your application that you want to record, set the trigger value to zero:

adb shell setprop debug.angle.capture.trigger 0

In logcat we'll see another entry corresponding to this:

ANGLE   : INFO: Capture triggered after frame 30440 for 10 frames

The app may pause briefly when the capture is completing. You can check its progress by looking at the file system:

adb shell ls -la /sdcard/Android/data/$PACKAGE_NAME/angle_capture

Allow the app to run until the logcat entry indicating the end of the API capture. The app should continue rendering after that:

ANGLE   : INFO: Finished recording graphics API capture

Optionally trigger additional captures

It is possible to capture an arbitrary number of traces.

After each trace completes, set the trigger value to the desired number of frames to capture for the next trace, optionally create and specify a different out_dir for the new trace data, and then start the new trace by again resetting the trigger value to zero.

Example workflow for multiple captures:

adb shell mkdir -p /data/data/$PACKAGE_NAME/angle_capture_1
adb shell mkdir -p /data/data/$PACKAGE_NAME/angle_capture_2
adb shell mkdir -p /data/data/$PACKAGE_NAME/angle_capture_3

# Set initial output dir and frame count
adb shell setprop debug.angle.capture.out_dir /data/data/$PACKAGE_NAME/angle_capture_1
adb shell setprop debug.angle.capture.trigger 100

# Trigger capture
adb shell setprop debug.angle.capture.trigger 0

# Set the next output dir and frame count
adb shell setprop debug.angle.capture.out_dir /data/data/$PACKAGE_NAME/angle_capture_2
adb shell setprop debug.angle.capture.trigger 30

# Trigger capture
adb shell setprop debug.angle.capture.trigger 0

# Set the next output dir and frame count
adb shell setprop debug.angle.capture.out_dir /data/data/$PACKAGE_NAME/angle_capture_3
adb shell setprop debug.angle.capture.trigger 60

# Trigger capture
adb shell setprop debug.angle.capture.trigger 0

# Pull the traces
adb pull /data/data/$PACKAGE_NAME/angle_capture_1
adb pull /data/data/$PACKAGE_NAME/angle_capture_2
adb pull /data/data/$PACKAGE_NAME/angle_capture_3

Note that multiple captures are incompatible with applications using persistent coherent memory. If more than one capture is attempted in this situation the tracer will exit immediately. The initial capture will remain valid.

End the capture early

If the application doesn't have a clear known ending frame, use debug.angle.capture.end_capture.

Set frame_start. frame_end is irrelevant for ending the capture early.

adb shell setprop debug.angle.capture.frame_start 1

Set end_capture to any number greater than 0. The value doesn't matter, as long as it's greater than 0.

adb shell setprop debug.angle.capture.end_capture 1

Run the application. At the moment you want the capture to be done, set end_capture to 0

adb shell setprop debug.angle.capture.end_capture 0

This will capture everything up to the time you triggered the end of the capture.

Pull the trace files

Next, we want to pull those files over to the host and run some scripts.

cd $CHROMIUM_SRC/third_party/angle/src/tests/restricted_traces
mkdir -p $LABEL
adb pull /sdcard/Android/data/$PACKAGE_NAME/angle_capture/. $LABEL/

Add the new trace to the JSON list

The list of traces is tracked in restricted_traces.json. Manually add your new trace to this list. Use version "1" for the trace version.

On Linux, you can also use a tool called jq to update the list. This ensures we get them in alphabetical order with no duplicates. It can also be done by hand if you are unable to install it, for some reason.

sudo apt-get install jq

Then run the following command:

export VERSION=1
jq ".traces = (.traces + [\"$LABEL $VERSION\"] | unique)" restricted_traces.json | sponge restricted_traces.json

Run code auto-generation

The gen_restricted_traces script auto-generates entries in our checkout dependencies to sync restricted trace data on checkout. To trigger code generation run the following from the angle root folder:

python ./scripts/run_code_generation.py

After this you should be able to git diff and see changes in the following files:

  • DEPS
  • scripts/code_generation_hashes/restricted_traces.json
  • src/tests/restricted_traces/restricted_traces.json (this is the file you originally modified)

Note the absence of the traces themselves listed above. They are automatically ignored by .gitignore since they won't be checked in directly to the repo.

Upload your trace to CIPD

Once you feel good about your trace, you can upload it to our collection of traces. This can only be done by Googlers with write access to the trace CIPD prefix. If you need write access contact someone listed in the OWNERS file.

Please kindly go over the trace content with ANGLE code owners before running below commands. You can share your trace through Google Drive for content iterations. We cannot delete trace files once they are up on the CIPD. Doing additional rounds of content check can help us save CIPD resources.

src/tests/restricted_traces/sync_restricted_traces_to_cipd.py

Upload your CL

Ensure your current working directory is up-to-date, and upload:

git cl upload

You're now ready to run your new trace on CI!

Comparing screenshots against the native driver

To compare trace screenshots from ANGLE vs the native driver, you can use the compare_trace_screenshots.py script.

The following steps will work on Android, but are transferrable to any operating system.

First, make a spot for the results:

adb shell rm -r /sdcard/angle/screenshots
adb shell mkdir -p /sdcard/angle/screenshots

Then run the traces using ANGLE:

out/AndroidPerformance/angle_trace_tests --verbose --run-to-key-frame --screenshot-dir /sdcard/angle/screenshots --shard-timeout 1000000

And again with the native driver:

out/AndroidPerformance/angle_trace_tests --verbose --run-to-key-frame --screenshot-dir /sdcard/angle/screenshots --shard-timeout 1000000 --use-gl=native

It may take a few tries as some drivers will crash. In that case, run the ones at the end that were stragglers, i.e.:

out/AndroidPerformance/angle_trace_tests --verbose --run-to-key-frame --screenshot-dir /sdcard/angle/screenshots --shard-timeout 1000000 --use-gl=native --gtest_filter="*words*:*world*:*worms*:*zenonia*:*zillow*:*zombie*"

Pull the screenshots:

adb pull /sdcard/angle/screenshots
cd screenshots

And run the compare script:

python3 ../src/tests/restricted_traces/compare_trace_screenshots.py versus_native --screenshot-dir . --trace-list-path ../src/tests/restricted_traces/

The script will print out results comparing ANGLE vs. native screenshots at different fuzz factors. It may also print out NA for missing screenshots:

...
arknights angle_vulkan_arknights.png MISSING_EXT.png NA NA NA NA NA NA
asphalt_8 angle_vulkan_asphalt_8.png angle_native_asphalt_8.png 641849 222157 116426 1701 82 22
asphalt_9 angle_vulkan_asphalt_9.png angle_native_asphalt_9.png 17919 420 305 293 232 3
...

Script will also save difference PNG files for each fuzz factor into the --screenshot-dir. These files will be saved even if there is no difference. To discard such files you may add --discard_zero_diff_png (or -d) argument before the versus_native command.

Comparing screenshots in two directories at different fuzz factors

In some cases it may be useful to compare screenshots in two directories. For example: to compare different runs on the same device, different loops of the same replay run, runs on different devices, and so on.

After you have prepared screenshots for comparison, run the fuzz_ab command:

python3 compare_trace_screenshots.py -d fuzz_ab --a_dir /my/trace/a --b_dir /my/trace/b --out /my/trace/diff

It will compare screenshots in these directories at different fuzz factors (similar to the versus_native command). In this example -d (--discard_zero_diff_png) argument was added to only keep PNG files with the difference.

Command also has --relaxed_file_list_match (-r) argument, allowing to compare directories with at least single match, which may be handy in some situations.

Upgrading existing traces

With tracer updates sometimes we want to re-run tracing to upgrade the trace file format or to take advantage of new tracer improvements. The retrace_restricted_traces script allows us to re-run tracing using SwiftShader on a desktop machine. As of writing we require re-tracing on a Windows machine because of size limitations with a Linux app window.

Part 1: Retrace it

Upgrade your trace into a new directory called retrace-wip

In this instance, we'll upgrade octopath_traveler

export TRACE_GN_PATH=out/Debug
export TRACE_NAME=octopath_traveler
src/tests/restricted_traces/retrace_restricted_traces.py upgrade $TRACE_GN_PATH retrace-wip -f $TRACE_NAME

Interleaved client attribute analysis

Apps can use client attribute arrays without binding to the array buffer (e.g., via glVertexAttribPointer()) to draw. The capture tool has been updated to detect interleaved client vertex attributes, i.e., vertex attributes that use the same client array data at different offsets for draw. In that case, the client array data is captured along with the offsets for each attribute. However, this will not be reflected on the traces captured before this feature was introduced. In those traces, each client attribute data is recorded as a separate attribute array (gClientArrays[]) and treated as an attribute separate from the rest, which can result in different behavior between the trace and the real app (such as instruction count).

For example, take a draw using three interleaved client array pointers, each using a 4-byte float value.

  • In the real app, this would look like three glVertexAttribPointer() calls with the pointer set to ptr, ptr + 4 and ptr + 8.
  • However, before this feature was introduced in the capture tool, these attributes would be recorded as gClientArrays[0], gClientArrays[1], and gClientArrays[2].

The script check_attribute_interleaving.py has been added to close the gap further between the trace and the real app, which the retracing script will use during an upgrade to analyze the client array attribute pointers in the trace (gClientArrays[]) and their corresponding data. Its goal is to detect and restore the interleaved property of such attributes.

If the attributes were found to have matching data with an offset, it will print a notification indicating the existence of such cases in the existing trace. However, it will not try to merge those attributes yet. To apply the attribute merges to the trace code during the upgrade, the flag -m or --merge-attributes should be used for the retracing script:

src/tests/restricted_traces/retrace_restricted_traces.py upgrade $TRACE_GN_PATH retrace-wip -m -f $TRACE_NAME

After this, the attributes determined to be part of the same client array are updated to use the same unified data with their respective offsets.

Note that the script check_attribute_interleaving.py can also be used as a standalone tool to analyze trace code for potential interleaved client attributes.

Part 2: Verify it

Before we check in an upgraded trace, we want to put it through enough paces to ensure behaves the same or better.

Screenshots

For screenshots, we want to verify all frames render correctly before and after Reset.

So make two spots to gather the screenshots, and one to gather results:

mkdir retrace-wip/${TRACE_NAME}_before
mkdir retrace-wip/${TRACE_NAME}_after
mkdir retrace-wip/${TRACE_NAME}_compare

We need two loops to verify Reset, so you'll need to inspect how many frames are in the trace. In this case, octopath_traveler has 500 frames, so we need 1000 screenshots. We use -1 as the screenshot frame so we get all images:

export FRAME_COUNT=1000
out/Debug/angle_trace_tests --gtest_filter=TraceTest.${TRACE_NAME} --use-angle=swiftshader --max-steps-performed ${FRAME_COUNT} --screenshot-dir retrace-wip/${TRACE_NAME}_before --screenshot-frame -1

Then move the new trace in and run it again:

mv src/tests/restricted_traces/${TRACE_NAME} retrace-wip/${TRACE_NAME}_orig
cp -r retrace-wip/${TRACE_NAME} src/tests/restricted_traces
autoninja -C out/Debug angle_trace_tests
out/Debug/angle_trace_tests --gtest_filter=TraceTest.${TRACE_NAME} --use-angle=swiftshader --max-steps-performed ${FRAME_COUNT} --screenshot-dir retrace-wip/${TRACE_NAME}_after --screenshot-frame -1

After that, we have a script that will compare the before and after screenshots, saving the results:

vpython3 src/tests/restricted_traces/compare_trace_screenshots.py versus_upgrade --before retrace-wip/${TRACE_NAME}_before --after retrace-wip/${TRACE_NAME}_after --outdir retrace-wip/${TRACE_NAME}_compare

If you have any diffs, they will pop out like this, and you need to investigate:

angle_vulkan_swiftshader_octopath_traveler_frame1.png 0
angle_vulkan_swiftshader_octopath_traveler_frame10.png 0
angle_vulkan_swiftshader_octopath_traveler_frame100.png 1.12185e+06
Pixel diff detected!

Performance

We need to ensure we're getting the same frame times and memory usage.

The easiest way to do that is on Android, which can show us GPU and CPU memory.

First, restore the original trace, then build and install the most optimized build:

rm -r src/tests/restricted_traces/${TRACE_NAME}
cp -r retrace-wip/${TRACE_NAME}_orig src/tests/restricted_traces/${TRACE_NAME}
autoninja -C out/AndroidPerformance angle_trace_tests

Then run the restricted_trace_perf.py script to gather frame times and memory:

pushd src/tests/restricted_traces
vpython3 restricted_trace_perf.py --fixedtime 10 --sleep 10 --memory --cpu-inst user_and_kernel --output-tag ${TRACE_NAME}.before --loop-count 5 --build-dir ../../../out/AndroidPerformance --renderer vulkan --filter ${TRACE_NAME}
popd

You should get output like this:

trace                                    wall_time       gpu_time        frame_wall_time cpu_time        gpu_power  cpu_power  infra_power gpu_mem_sustained    gpu_mem_peak    proc_mem_median      proc_mem_peak   process_cpuinst      gfxlib_cpuinst       angle_cpuinst        vulkan_cpuinst       gles_cpuinst         libc_cpuinst

Starting run 1 with vulkan at 2023-08-17 16:26:29

vulkan_octopath_traveler                 2.8125          0               2.0213284872    2.6833208333    0.000      0.000      0.000      157458432            157458432       581324000            581536000       9814450.073333334    1907805.1666666667   30495.19861111111    0.0                  1877309.9680555556   9814093.243888889

Starting run 2 with vulkan at 2023-08-17 16:26:54

vulkan_octopath_traveler                 2.7942          0               2.0026349672    2.6582661111    0.000      0.000      0.000      157167616            157167616       580976000            581120000       9940974.378611112    1930372.9425         29421.109166666665   0.0                  1900951.8333333333   9940970.091666667

Starting run 3 with vulkan at 2023-08-17 16:27:18

vulkan_octopath_traveler                 2.8087          0               2.0104668258    2.6753233333    0.000      0.000      0.000      155391744            155398144       578784000            578844000       9849789.568611111    1897764.1875         27965.308333333334   0.0                  1869798.8791666667   9849162.080555556

Starting run 4 with vulkan at 2023-08-17 16:27:42

vulkan_octopath_traveler                 2.8126          0               2.0338224075    2.6839755556    0.000      0.000      0.000      148413982            157356032       580764000            580808000       9858647.521944445    1891151.5491666666   27062.17777777778    0.0                  1864089.371388889    9857876.606944444

Starting run 5 with vulkan at 2023-08-17 16:28:05

vulkan_octopath_traveler                 2.8193          0               2.0375366431    2.6894483333    0.000      0.000      0.000      148760576            148770816       572796000            572820000       9813130.877222221    1892703.2255555557   25800.17             0.0                  1866903.0555555555   9812411.621388888

Bring in the upgraded trace, build and install the trace again:

rm -rf src/tests/restricted_traces/${TRACE_NAME}
cp -r retrace-wip/${TRACE_NAME} src/tests/restricted_traces/${TRACE_NAME}
autoninja -C out/AndroidPerformance angle_trace_tests

And collect performance data:

vpython3 restricted_trace_perf.py --fixedtime 10 --sleep 10 --memory --cpu-inst user_and_kernel --output-tag ${TRACE_NAME}.after --loop-count 5 --build-dir ../../../out/AndroidPerformance --renderer vulkan --filter ${TRACE_NAME}

Verify using a spreadsheet that the values are relatively the same. If you notice a marked difference, spend some time understanding it. For instance, you may see memory decrease due to fixed in the upgrade.

Part 3: Test the upgraded traces under an experimental prefix

To test the trace on all platforms, we first upload them to a temporary CIPD path for testing. After a successful run on the CQ, we will then upload them to the main ANGLE prefix.

To enable the experimental prefix, edit restricted_traces.json to use a version number beginning with 'x'. For example:

  "traces": [
    ...
    "octopath_traveler x1",
    ...

Then run:

vpython3 src/tests/restricted_traces/sync_restricted_traces_to_cipd.py --filter ${TRACE_NAME}
vpython3 scripts/run_code_generation.py

After these commands complete succesfully, create and upload a CL as normal.

git cl upload

Before running tests, you need to grant the bots access to your experimental CIPD files (substituting your account name):

cipd acl-edit experimental/google.com/$USERNAME -reader user:angle-try-builder@chops-service-accounts.iam.gserviceaccount.com
cipd acl-edit experimental/google.com/$USERNAME -reader user:chromium-try-gpu-builder@chops-service-accounts.iam.gserviceaccount.com

You can verify it worked by running this command and seeing the bot added to readers:

cipd acl-list experimental/google.com/$USERNAME/angle/traces
...
Readers:
  via "experimental/google.com/$USERNAME":
    user:angle-try-builder@chops-service-accounts.iam.gserviceaccount.com
    user:chromium-try-gpu-builder@chops-service-accounts.iam.gserviceaccount.com

Run CQ +1 Dry-Run. If you find a test regression, see the section below on diagnosing tracer errors. Otherwise proceed with the steps below.

Part 4: Upload the verified traces to CIPD under the stable prefix

Now that you've validated the traces on the CQ, update restricted_traces.json to remove the 'x' prefix and incrementing the version of the traces (skipping versions if you prefer) and then run:

vpython3 src/tests/restricted_traces/sync_restricted_traces_to_cipd.py --filter ${TRACE_NAME}
vpython3 scripts/run_code_generation.py

Then create and upload a CL as normal. Congratulations, you've finished the trace upgrade!

Finding a trace's minimum requirements

retrace_restricted_traces.py can be used to determine a trace's minimum extensions and GLES version. Run the command:

src/tests/restricted_traces/retrace_restricted_traces.py get_min_reqs $TRACE_GN_PATH [--traces "*"]

The script will run each listed trace multiple times so it can find the minimum required GLES version and each required extension. Finally it records that information to the trace's json file.

By default it will run with SwiftShader. To make the script use your machine's native vulkan drivers, use the --no-swiftshader argument before the script's command:

src/tests/restricted_traces/retrace_restricted_traces.py --no-swiftshader get_min_reqs $TRACE_GN_PATH [--traces "*"]

If retracing an existing trace, any associated addExtensionPrerequisite() calls must be removed from TracePerfTest.cpp and the tracename.json file must be made writable.

Traces are run with all extensions enabled by default. It may be useful to test with only a subset of extensions. This can be done by adding the --request-extensions argument to angle_trace_tests. Multiple extensions must be contained by quotation marks and only a single space can be used as a separator. To run with no extensions enabled, specify a null list -- "":

./out/Debug/angle_trace_tests --gtest_filter=*tracename --request-extensions "EXT_color_buffer_float GL_EXT_texture_filter_anisotropic"

or

./out/Debug/angle_trace_tests --gtest_filter=*tracename --request-extensions ""

Extended testing and full trace upgrades

If you want to really drill down on trace differences, you might want to use the built in validation support, which serailizes the internal state of ANGLE.

Prep work: Back up existing traces

This will save the original traces in a temporary folder if you need to revert to the prior trace format:

src/tests/restricted_traces/retrace_restricted_traces.py backup "*"

Note: on Linux, remove the command py prefix to the Python scripts.

This will save the traces to ./retrace-backups. At any time you can revert the trace files by running:

src/tests/restricted_traces/retrace_restricted_traces.py restore "*"

Part 1: Upgrading Sanity Check with T-Rex

First we'll retrace a single app to verify the workflow is intact. Please ensure you replace the specified variables with paths that work on your configuration and checkout:

Step 1/3: Capture T-Rex with Validation

export TRACE_GN_PATH=out/Debug
export TRACE_NAME=trex_200
src/tests/restricted_traces/retrace_restricted_traces.py upgrade $TRACE_GN_PATH retrace-wip -f $TRACE_NAME --validation --limit 3

The --validation flag will turn on additional validation checks in the trace. The --limit 3 flag forces a maximum of 3 frames of tracing so the test will run more quickly. The trace will end up in the retrace-wip folder.

Step 2/3: Validate T-Rex

The command below will update your copy of the trace, rebuild, the run the test suite with validation enabled:

src/tests/restricted_traces/retrace_restricted_traces.py validate $TRACE_GN_PATH retrace-wip $TRACE_NAME

If the trace failed validation, see the section below on diagnosing tracer errors. Otherwise proceed with the steps below.

Step 3/3: Restore the Canonical T-Rex Trace

src/tests/restricted_traces/retrace_restricted_traces.py restore $TRACE_NAME

Part 2: Do a limited trace upgrade with validation enabled

Step 1/3: Upgrade all traces with a limit of 3 frames

src/tests/restricted_traces/retrace_restricted_traces.py upgrade $TRACE_GN_PATH retrace-wip --validation --limit 3  --no-overwrite

If this process gets interrupted, re-run the upgrade command. The --no-overwrite argument will ensure it will complete eventually.

If any traces failed to upgrade, see the section below on diagnosing tracer errors. Otherwise proceed with the steps below.

Step 2/3: Validate all upgraded traces

src/tests/restricted_traces/retrace_restricted_traces.py validate $TRACE_GN_PATH retrace-wip "*"

If any traces failed validation, see the section below on diagnosing tracer errors.

Step 3/3: Restore all traces

src/tests/restricted_traces/retrace_restricted_traces.py restore "*"

Part 3: Do the full trace upgrade

rm -rf retrace-wip
src/tests/restricted_traces/retrace_restricted_traces.py upgrade $TRACE_GN_PATH retrace-wip --no-overwrite

If this process gets interrupted, re-run the upgrade command. The --no-overwrite argument will ensure it will complete eventually.

If any traces failed to upgrade, see the section below on diagnosing tracer errors.

Otherwise, use the steps above to verify and upgrade your traces.

Diagnosing and fixing tracer errors

Debugging a crash or GLES error

Ensure you're building ANGLE in Debug. Then look in the retrace script output to find the exact command line and environment variables the script uses to produce the failure. For example:

INFO:root:ANGLE_CAPTURE_LABEL=trex_200 ANGLE_CAPTURE_OUT_DIR=C:\src\angle\retrace-wip\trex_200 ANGLE_CAPTURE_FRAME_START=2 ANGLE_CAPTURE_FRAME_END=4 ANGLE_CAPTURE_VALIDATION=1 ANGLE_FEATURE_OVERRIDES_ENABLED=allocateNonZeroMemory:forceInitShaderVariables out\Debug\angle_trace_tests.exe --gtest_filter=TraceTest.trex_200 --use-angle=swiftshader --max-steps-performed 3 --retrace-mode

Once you can reproduce the issue you can use a debugger or other standard debugging processes to find the root cause and a fix.

Debugging a serialization difference

If you encouter a serialization mismatch in the retrace, you can find the complete serialization output by looking in the retrace script output. ANGLE saves the complete serialization file contents on any mismatch. You can inspect and diff these files in a text editor to help diagnose what objects are faulty.

If the mismatch is with a Buffer or Texture object content, you can manually edit the frame_capture_utils.cpp file to force some or all of the objects to serialize their entire contents. This can help show what kind of pixel or data differences might be causing the issue. For example, change this line:

json->addBlob("data", dataPtr->data(), dataPtr->size());

to

json->addBlobWithMax("data", dataPtr->data(), dataPtr->size(), 1000000);

Note: in the future, we might make this option exposed via an envioronment variable, or even allow serialization of entire data blocks in text-encoded form that could be decoded to separate files.

If you still can't determine what code might be causing the state difference, we can insert finer-grained serialization checkpoints to "bisect" where the coding mismatch is happening. It is not possible to force checkpoints after every GLES call, because serialization and validation is so prohibitively expensive. ANGLE instead has feature in the tracer that allows us to precisely control where the tracer inserts and validates the checkpoints, by using a boolean expression language.

The retrace script command --validation-expr allows us to specify a C-like expression that determines when to add serialization checkpoints. For example, we can specify this validation expression:

((frame == 2) && (call < 1189) && (call > 1100) && ((call % 5) == 0))

Using this expression will insert a serialization checkpoint in the second frame, on every 5th captured call, and when the captured call count is between 1101 and 1188. Here the call keyword denotes the call counter, which resets to 1 every frame, and increments by 1 with every captured GLES API call. The frame keyword denotes the frame counter, which starts at 1 and increments by 1 every captured frame. The expression syntax supports all common C boolean operators.

By finding a starting and ending frame range, and narrowing this range through experimentation, you can pinpoint the exact call that triggers the serialization mismatch, and then diagnose and fix the root cause. In some cases you can use RenderDoc or other frame debugging tools to inspect resource states before/after the bad call once you have found it.

See also: http://crrev.com/c/3136094

Debugging a pixel test failure without a serialization mismatch

Sometimes you manage to complete validation and upload, just to find a golden image pixel difference that manifests in some trace configurations. These problems can be harder to root cause. For instance, some configurations may render undefined pixels that are in practice well-defined on most GLES implementations.

The pixel differences can also be a product of mismatched state even if the trace validation says all states are matched. Because ANGLE's GLES state serialization is incomplete, it can help to check the state serialization logic and add missing features as necessary.