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Is It Easy to Capture Mobile Pphone Packets

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Devices running Android 9 (API level 28) or higher include a system-level app called System Tracing. This app is similar to the systrace command-line utility, but the app allows you to record traces directly from a test device itself, without needing to plug in the device and connect to it over ADB. You can then use the app to share results from these traces with your development team.

It's particularly helpful to record traces when addressing performance-related bugs in your app, such as slow startup, slow transitions, or UI jank.

Record a system trace

The System Tracing app allows you to record a system trace using a Quick Settings tile or a menu within the app itself. The following sections describe how to complete the recording process using these interfaces.

Record using Quick Settings tile

The Quick Settings tile is usually the more convenient way to complete the on-device system tracing process.

Set up tile

Figure 2. The Show Quick Settings tile switch in the System Tracing app

If you're using System Tracing for the first time on your test device, or if you don't see the System Tracing tile in your device's Quick Settings panel (Figure 1), complete the following setup steps:

  1. Enable developer options, if you haven't done so already.
  2. Open the Developer Options settings screen.
  3. In the Debugging section, select System Tracing. The System Tracing app opens, showing the app menu.

  4. From the app menu, enable Show Quick Settings tile, as shown in Figure 2. The system adds the System Tracing tile to the Quick Settings panel, which appears in Figure 1:

    Figure 1. The System Tracing tile within the Quick Settings panel

    Note: By default, the system adds the System Tracing tile as the first tile in the Quick Settings panel. If you'd like the tile to appear in a different position, use the panel's edit mode to move the tile.

Complete a system trace recording

To record a system trace using the Quick Settings panel, complete the following steps:

  1. Tap the System Tracing tile, which has the label "Record trace". The tile becomes enabled, and a persistent notification appears to notify you that the system is now recording a trace, as shown in Figure 3:

    Notification with the message 'Trace is being recorded. Tap to stop tracing.'
    Figure 3. Persistent notification that appears after starting an on-device system trace

  2. Perform the actions in your app that you'd like the system to inspect.

  3. When you've completed these actions, stop tracing by tapping either the System Tracing tile in the Quick Settings panel or on the System Tracing notification.

    The system displays a new notification that contains the message "Saving trace". When saving is complete, the system dismisses the notification and displays a third notification, confirming that your trace has been saved and that you're ready to share the system trace, as shown in Figure 4:

    Notification with the message 'Trace saved. Tap to share your trace.'
    Figure 4. Persistent notification that appears after the system has finished saving a recorded trace

The app menu allows you to configure several advanced settings related to system tracing and provides a switch for starting and stopping a system trace.

To record a system trace using the System Tracing app menu, complete the following steps:

  1. Enable developer options, if you haven't done so already.

  2. Open the Developer Options settings screen. In the Debugging section, select System Tracing. The System Tracing app opens.

    Alternatively, if you've set up the System Tracing tile, you can long-tap on the tile to enter the System Tracing app.

  3. Make sure Trace debuggable applications is selected to include applications that have debugging enabled in the system trace.

  4. Optionally, choose the Categories of system and sensor calls to trace, and choose a Per-CPU buffer size (in KB). Choose categories that correspond to the use case that you're testing, such as the Audio category for testing Bluetooth operations or the Memory category for heap allocations.

    Figure 5. The Record trace switch in the System Tracing app

  5. Optionally, select Long traces to enable traces that are saved continuously to device storage. For this option, you must set limits for the Maximum long trace size and Maximum long trace duration.

  6. Enable the Record trace switch, highlighted in Figure 5. The tile becomes enabled, and a persistent notification appears to notify you that the system is now recording a trace (Figure 3).

  7. Perform the actions in your app that you'd like the system to inspect.

  8. When you've completed these actions, stop tracing by disabling the Record trace switch.

    The system displays a new notification that contains the message "Saving trace". When saving is complete, the system dismisses the notification and displays a third notification, confirming that your trace has been saved and that you're ready to share the system trace, as shown in Figure 4.

The System Tracing app helps you share system trace results as part of several different workflows. On a device running Android 10 (API level 29) or later, trace files are saved with the .perfetto-trace filename extension and can be opened in the Perfetto UI. On a device running an earlier version of Android, trace files are saved with the .ctrace filename extension, which denotes the Systrace format.

System Tracing allows you to share your collected trace with other apps on your device. In doing so, you can send the trace to your development team through an email or a bug-tracking app without needing to connect a device to your development machine.

After you've recorded a system trace, tap on the notification that appears on the device (see Figure 4). The platform's intent picker appears, allowing you to share your trace using the messaging app of your choice.

On devices running Android 10 (API level 29), traces are shown in the Files app. If desired, you can share a trace from this app.

Download report using ADB

If desired, you can also extract a system trace from a device using ADB. Connect the device that recorded the trace to your development machine, then run the following commands in a terminal window:

cd /path-to-traces-on-my-dev-machine          && \   adb pull /data/local/traces/ .

Converting between trace formats

You can convert Perfetto trace files to the Systrace format. See Converting between trace formats for more information.

Create an HTML report

When sharing your trace, the report itself resides in a .perfetto-trace file (on devices running Android 10 or higher) or a .ctrace file (for all other versions).

Create an HTML report from the trace file using a web-based UI or from the command line.

Web-based UI

Use the Perfetto UI to open the trace file and generate the report.

For a Perfetto file, click Open trace file. For a Systrace file, click Open with legacy UI. The legacy UI has the same look and feel as the Systrace report.

Command line

Run the following commands in a terminal window to generate an HTML report from the trace file:

cd /path-to-traces-on-my-dev-machine          && \   systrace --from-file          trace-file-name{.ctrace | .perfetto-trace}

If you don't already have the systrace command-line program, you can download it from the Catapult project on GitHub, or directly from the Android Open Source Project.

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Source: https://developer.android.com/topic/performance/tracing/on-device

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