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diff --git a/catapult/devil/docs/persistent_device_list.md b/catapult/devil/docs/persistent_device_list.md new file mode 100644 index 00000000..d08d9a9e --- /dev/null +++ b/catapult/devil/docs/persistent_device_list.md @@ -0,0 +1,41 @@ +<!-- Copyright 2016 The Chromium Authors. All rights reserved. + Use of this source code is governed by a BSD-style license that can be + found in the LICENSE file. +--> + +# Devil: Persistent Device List + +## What is it? + +A persistent device list that stores all expected devices between builds. It +is used by the perf test runner in order to properly shard tests by device +affinity. This is important because the same performance test can yield +meaningfully different results when run on different devices. + +## Bots + +The list is usually located at one of these locations: + + - `/b/build/site_config/.known_devices`. + - `~/.android`. + +Look at recipes listed below in order to find more up to date location. + +## Local Runs + +The persistent device list is unnecessary for local runs. It is only used on the +bots that upload data to the perf dashboard. + +## Where it is used + +The persistent device list is used in performance test recipes via +[api.chromium\_tests.steps.DynamicPerfTests](https://cs.chromium.org/chromium/build/scripts/slave/recipe_modules/chromium_tests/steps.py?q=DynamicPerfTests). +For example, the [android/perf](https://cs.chromium.org/chromium/build/scripts/slave/recipes/android/perf.py) recipe uses it like this: + +```python +dynamic_perf_tests = api.chromium_tests.steps.DynamicPerfTests( + builder['perf_id'], 'android', None, + known_devices_file=builder.get('known_devices_file', None)) +dynamic_perf_tests.run(api, None) +``` + |