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.
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.
The persistent device list is unnecessary for local runs. It is only used on the bots that upload data to the perf dashboard.
The persistent device list is used in performance test recipes via api.chromium_tests.steps.DynamicPerfTests. For example, the android/perf recipe uses it like this:
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)