TRACED_PROBES(8)

NAME

traced_probes - System & OS Probes

DESCRIPTION

traced_probes is a specialized daemon that acts as a privileged Producer in the Perfetto architecture. While any application can act as a producer to contribute its own trace data, traced_probes is specifically responsible for collecting system-level and kernel-level data that typically requires elevated privileges.

Relationship with traced

traced_probes is a client of the traced service. It connects to traced's producer socket and registers a set of data sources. traced then sends requests to traced_probes to start or stop these data sources as part of a tracing session.

This separation of concerns is a key part of Perfetto's design. traced is the central manager, while traced_probes is a specialized data provider. This decoupled architecture allows for multiple, independent producers and consumers to interact with the tracing system simultaneously without interfering with each other.

Security and Privileges

traced_probes often needs to run with elevated privileges (e.g., root or system user on Android) to access kernel interfaces like debugfs or /proc. Separating these high-privilege probes into their own daemon is a key part of Perfetto's security model. It ensures that only a minimal amount of code runs with high privileges, adhering to the principle of least privilege.

Configuration

The data sources provided by traced_probes are configured within the main trace configuration protobuf that is sent to traced. For example, to enable ftrace, you would include an FtraceConfig within the DataSourceConfig for the linux.ftrace data source.

Data Sources

traced_probes provides a wide range of data sources, collecting system-level and kernel-level data. The configuration for these data sources is specified in the data_sources section of the overall trace configuration. Each data source has its own configuration message within a data_source_config block.

Here is an example of the general structure:

Below is a detailed list of the main data sources provided by traced_probes, separated by platform.

Linux Data Sources

These data sources are available on Linux-based systems, including Android.

Here is an example of a trace config enabling several Linux data sources:

linux.ftrace (Kernel Tracing)

• Description: This is the primary data source for high-frequency kernel events. It enables and reads raw ftrace data from the Linux kernel's ftrace interface, providing insights into process scheduling, system calls, interrupts, and other kernel activities.
• Configuration Example:data_sources: { config { name: "linux.ftrace" ftrace_config { ftrace_events: "sched/sched_switch" ftrace_events: "power/cpu_idle" ftrace_events: "sched/sched_waking" } } }
• Configuration: Configured via FtraceConfig within the DataSourceConfig. Key options include:
  • ftrace_events: List of ftrace events to enable (e.g., sched/sched_switch).
  • atrace_categories, atrace_apps: For Android, enables userspace Atrace categories and apps.
  • syscall_events: Specific syscalls to trace.
  • enable_function_graph: Enables kernel function graph tracing.
  • compact_sched: Enables compact encoding for scheduler events.
  • symbolize_ksyms: Enables kernel symbolization.
  • print_filter: Filters ftrace/print events based on content.

linux.process_stats (Process and Thread Statistics)

• Description: Collects detailed process and thread-level statistics from the /proc filesystem. It provides both a snapshot of the process tree and periodic memory/CPU counters.
• Configuration Example:data_sources: { config { name: "linux.process_stats" process_stats_config { scan_all_processes_on_start: true proc_stats_poll_ms: 1000 } } }
• Configuration: Configured via ProcessStatsConfig. Key options include:
  • record_thread_names: Record thread names.
  • scan_all_processes_on_start: Dump the entire process tree at the start.
  • resolve_process_fds: Resolve file descriptor paths.
  • scan_smaps_rollup: Read /proc/[pid]/smaps_rollup.
  • record_process_age: Record process start time.
  • record_process_runtime: Record user and kernel mode CPU times.
  • record_process_dmabuf_rss: Record DMA buffer RSS.
  • proc_stats_poll_ms: Polling interval for periodic stats.
  • proc_stats_cache_ttl_ms: Time-to-live for cached stats.
  • quirks: Special behaviors (e.g., DISABLE_ON_DEMAND).

linux.sys_stats (System-Wide Statistics)

• Description: Collects system-wide statistics by periodically polling various files in /proc and /sys.
• Configuration Example:data_sources: { config { name: "linux.sys_stats" sys_stats_config { meminfo_period_ms: 1000 vmstat_period_ms: 1000 stat_period_ms: 1000 } } }
• Configuration: Configured via SysStatsConfig. Allows fine-grained control over which counters to collect and their polling frequencies (e.g., meminfo_period_ms, vmstat_period_ms, stat_counters).

linux.sysfs_power (Power and Battery Information)

• Description: Collects power and battery statistics using the Linux sysfs interface.
• Configuration Example:data_sources: { config { name: "linux.sysfs_power" } }
• Configuration: This data source does not have a specific configuration proto.

linux.inode_file_map (Inode to File Path Mapping)

• Description: Maps inode numbers to file paths, which is useful for correlating I/O events with the files being accessed.
• Configuration Example:data_sources: { config { name: "linux.inode_file_map" inode_file_config { scan_interval_ms: 10000 scan_delay_ms: 5000 scan_batch_size: 1000 } } }
• Configuration: InodeFileConfig allows specifying scan_mount_points, mount_point_mapping (to remap scan roots), scan_interval_ms, scan_delay_ms, scan_batch_size, and do_not_scan.

metatrace (Perfetto Self-Tracing)

• Description: A self-tracing data source that records events within Perfetto itself, useful for debugging and performance analysis of the tracing system.
• Configuration Example:data_sources: { config { name: "metatrace" } }
• Configuration: No specific configuration in DataSourceConfig.

linux.system_info (System Information)

• Description: Records general information about the system, such as CPU details and kernel version.
• Configuration Example:data_sources: { config { name: "linux.system_info" } }
• Configuration: No specific configuration in DataSourceConfig.

Android Data Sources

These data sources are available only on Android.

Here is an example of a trace config enabling several Android data sources:

android.power (Power and Battery Information)

• Description: Collects power and battery statistics using Android-specific HALs.
• Configuration Example:data_sources: { config { name: "android.power" android_power_config { battery_poll_ms: 1000 battery_counters: BATTERY_COUNTER_CHARGE battery_counters: BATTERY_COUNTER_CAPACITY_PERCENT collect_power_rails: true } } }
• Configuration: AndroidPowerConfig allows enabling specific battery counters (battery_counters), power rails (collect_power_rails), energy estimation breakdown (collect_energy_estimation_breakdown), and entity state residency (collect_entity_state_residency).

android.log (Android Logcat)

• Description: Streams log messages from Android's logcat buffer into the trace.
• Configuration Example:data_sources: { config { name: "android.log" android_log_config { log_ids: LID_DEFAULT log_ids: LID_SYSTEM min_prio: PRIO_INFO filter_tags: "ActivityManager" } } }
• Configuration: AndroidLogConfig allows filtering by log IDs (log_ids) and tags (filter_tags), and setting a minimum priority (min_prio).

android.system_property (Android System Properties)

• Description: Collects the state of Android system properties.
• Configuration Example:data_sources: { config { name: "android.system_property" android_system_property_config { poll_ms: 1000 property_name: "debug.tracing.screen_state" } } }
• Configuration: AndroidSystemPropertyConfig allows specifying property_names to monitor and a poll_ms interval.

android.packages_list (Android Package Information)

• Description: Dumps information about installed packages on Android.
• Configuration Example:data_sources: { config { name: "android.packages_list" packages_list_config { package_name_filter: "com.android.systemui" package_name_filter: "com.google.android.apps.nexuslauncher" } } }
• Configuration: PackagesListConfig allows filtering by package_name_filter and can be configured to only_write_on_cpu_use_every_ms (polling mode) or dump all at start.

android.game_interventions (Android Game Intervention List)

• Description: Dumps the game intervention list from the package manager on Android.
• Configuration Example:data_sources: { config { name: "android.game_interventions" android_game_intervention_list_config { package_name_filter: "com.example.mygame" } } }
• Configuration: AndroidGameInterventionListConfig allows filtering by package_name_filter.

android.cpu.uid (Per-UID CPU Time)

• Description: Collects per-UID CPU time from the kernel.
• Configuration Example:data_sources: { config { name: "android.cpu.uid" cpu_per_uid_config { poll_ms: 1000 } } }
• Configuration: CpuPerUidConfig allows setting the poll_ms interval.

android.kernel_wakelocks (Kernel Wakelocks)

• Description: Collects kernel wakelock information.
• Configuration Example:data_sources: { config { name: "android.kernel_wakelocks" kernel_wakelocks_config { poll_ms: 1000 } } }
• Configuration: KernelWakelocksConfig allows setting the poll_ms interval.

android.polled_state (Android Initial Display State)

• Description: Records the initial display state (e.g., screen on/off, brightness) on Android.
• Configuration Example:data_sources: { config { name: "android.polled_state" android_polled_state_config { poll_ms: 500 } } }
• Configuration: AndroidPolledStateConfig allows setting a poll_ms interval.

android.statsd (Android StatsD Atoms)

• Description: Collects StatsD atoms from the binder interface on Android.
• Configuration Example:data_sources: { config { name: "android.statsd" statsd_tracing_config { pull_config { pull_atom_id: 10000 # Example pull atom pull_frequency_ms: 1000 } push_atom_id: 10037 # Example push atom } } }
• Configuration: StatsdTracingConfig allows specifying pull_config (for pull atoms with frequency and packages) and push_atom_id (for push atoms).