Perfetto Release v51.1 CHANGELOG

[Lalit Maganti]

https://github.com/google/perfetto/tree/v51.1

v51.1 - 2025-06-26:
  Build system:
    * Fixed issue with Bazel copts/cxxopts. Embedders are required to add a
      default_cxxopts to their perfetto.bzl file in their repository.

v51.0 - 2025-06-24:
  Tracing service and probes:
    * Added a new data source to poll for CPU time per UID and cluster.
  SQL Standard library:
    * Added a new standard library table for filtering IRQ slices.
    * Added a new standard library module for Android's Low Memory Killer.
  Trace Processor:
    * Reworked core database engine to be more performant and better architected
      for future improvements.
    * Added new "trace summarization" functionality to trace processor as a more
      flexible replacement to old metrics system.
    * Added support for executing all available metrics when summarizing the
      trace with `--summary-metrics-v2 all`.
    * Added `trace_summary()` function to the Python API to execute the
      trace summaries and, specifically, v2 metrics.
    * Added support to adding SQL packages to Python API. This is the
      counterpart to the `--add-sql-package` shell option and allow loading SQL
      packages and modules from a filesystem path. These are then available to
      load using `INCLUDE PERFETTO MODULE` PerfettoSQL statements.
    * Improved handling of traces containing overlapping "complete" events
      (i.e. events with a duration, AKA 'X' events in the JSON format).
      While overlapping events are prohibited by the JSON spec, they do
      appear in many synthetically generated JSON traces. Previously, such
      events would break the data model of trace processor and cause significant
      glitches in the UI. These events are now dropped, fixing all the visual
      glitches and an error stat is emitted to make the user aware.
    * Improved performance of parsing JSON by 7x. JSON traces should now load
      much faster in the Perfetto UI and the trace processor.
  UI:
    * Improved JSON loading performance. See `Trace Processor` section above.
    * Improved duration based slice aggregators - slices are now trimmed to the
      width of the area selection.
    * Added the ability for users to set a custom timezone in the UI.
    * Added the ability to add descriptive text to tracks.
    * Added touchscreen support. The UI can now be used from tablets and other
      touch devices.
    * Removed the Viz page; it was an experiment which did not go anywhere.
  SDK:
    * Changed the implementation of TrackEvent to only have a single data source
      for multiple namespace; categories will be exported correctly only on
      recent perfetto tracing services that support UpdateDataSource.
    * Changed the priority of TrackEvent enabled/disabled category and tags.
      The new logic ranks (in this order)
      specific > pattern > single char "*" wildcard,
      categories (enabled > disabled) > tags (disabled > enabled).
  Docs:
    * Significantly improved the project's documentation with a team-wide
      collaboration to make it more user-friendly and up to date.