Unreleased:
  Tracing service and probes:
    *
  Trace Processor:
    *
  UI:
    *
  SDK:
    *

v29.0 - 2022-09-06:
  Tracing service and probes:
    * Add support for only tracing selected syscalls. By selecting only syscalls
      of interest, usage of the trace buffer and performance impact on device
      is reduced.
    * Add support for parsing DSI ftrace events.
  Trace Processor:
    * Make calling NotifyEndOfFile more than once an error: this was deprecated
      in v28. Flush should be used instead for all by the final call.
    * Add parsing and ingestion for V4L2 events.
    * Upgraded SQLite to 3.39.2.
  UI:
    * Add support for searching Android log events.
    * Group kernel wakelock tracks into a single track group.
  SDK:
    * Added support for startup tracing. Tracing can be started in an app
      before it connects to the tracing service.
      The data sources which are started for startup tracing, will
      be automatically adopted to normal tracing session once we start
      normal tracing session.
    * Added the |first_packet_on_sequence| boolean which is set the first packet
      emitted on each TraceWriter.


v28.0 - 2022-08-02:
  Tracing service and probes:
    * Add android.statsd datasource.
    * Removed log spam about sys.trace.traced_started in standalone builds.
    * Changed kallsyms parsing in traced_probes (ftrace) to be always
      synchronous (when starting the trace, rather than on the first batch).
    * Added ksyms_mem_policy = KSYMS_RETAIN_FOREVER config to avoid destroying
      and re-parsing kallsysm repeatedly in benchmark runs.
    * Improve heap profiling shutdown: now the shared memory buffer where
      alloc/free records are stored is properly flushed when stopping the data
      source.
    * Fixed race condition in the daemonization path of perfetto --background.
      It would cause daemonization failures if the TTY is destroyed immediately.
  Trace Processor:
    * Deprecate calling NotifyEndOfFile more than once: Flush should instead be
      used for all but the final call.
    * Added ingestion and visualization of I2C transactions.
  UI:
    * Changed callstack sampling selection: selecting one sample now only shows
      one stacktrace, selecting multiple samples shows the aggregation.
  SDK:
    * Fixed a bug (b/239725760) that would cause abstract sockets using the
      "@name" syntax in PERFETTO_CONSUMER_SOCK_NAME/PERFETTO_PRODUCER_SOCK_NAME
      to have a trailing \0 in the socket name. This breaks interoperability
      with adb forwarding. This is a tracing protocol breaking change. Nobody
      seems to be relying on @abstract syntax across different versions of
      client vs service.
    * Changed the mangling scheme for protozero enums nested in another message:
      instead of OuterClass_Enum_VALUE, the enum values will be just named
      VALUE with the enum itself wrapped in a perfetto_pbzero_enum_OuterClass
      namespace to prevent naming collisions. This will allow the users
      to alias the enum directly and use throughout their code.
      The exact name mangling scheme is a carry-over from libprotobuf and
      an internal implementation detail, so nobody should be relying on that.
    * Added protozero::EnumToString() to convert enum keys to string literals.


v27.1 - 2022-07-11:
  SDK:
    * Added an API for shutting down Perfetto.


v27.0 - 2022-07-01:
  Tracing service and probes:
    * Fix rare crash due to watchdog timeout being too short.
  Trace Processor:
    * Removed enable_perfetto_x64_cpu_opt by default for x64 MacOS
      since it caused issues for CIs.
    * Improved performance of filtering and sorting on most queries.
  UI:
    * Changed sorting of process groups to take slice count and presence of
      perf profiles into account.
  SDK:
    * 


v26.1 - 2022-06-13:
  Trace Processor:
    * Fixed build failures on Windows.


v26.0 - 2022-06-13:
  Tracing service and probes:
    * Added wildcard (*) support when targeting processes by their command line
      in the Android perf profiler ("linux.perf" data source) and Java heap
      snapshots ("android.java_hprof").
    * Added support for kernel thread sampling, and kernel-only callstacks in
      the Android perf profiler.
    * Fixed rare crash when parsing zero-length ftrace __data_loc strings.
    * Fixed rare crash on 4.19 kernel when encountering unexpected zero-padded
      ftrace pages.
    * Removed capturing of thread_time_in_state (per-UID, per-OOM-adj time).
      The data was unused and subsumed by correlating sched data with power
      rail monitors.
  Trace Processor:
    * Added CREATE_VIEW_FUNCTION operator to define a SQL function that can
      return a temporary table and yield multiple rows and columns.
    * Changed kernel threads to be represented as single-thread processes in
      Linux system traces. The (incorrect) legacy behaviour was to treat them
      as threads of the kthreadd process.
    * Added ABS_TIME_STR function which converts a trace timestamp to
      an ISO8601 string.
    * Added ingestion for phase='R' events, used by performance.{now,mark}().
    * Changed 'trace_to_text' to be named 'traceconv'. The source
      location also moved from 'tools/trace_to_text' to 'src/traceconv'.
    * Changed compiler flags, added -mavx2. The previous patch in v22.0 was
      supposed to add AVX2 support but added only AVX.
    * Changed the handling of the last per-cpu sched slices: rather than
      extending the last event to the end of the trace, the last scheduling
      event has a -1 duration. UIs are supposed to deal with visual extension.
    * Removed android_thread_time_in_state metric. It was an experiment and was
      unused.
    * Removed `instant` table. All instant events are now 0-duration events in
      the `slice` table.
    * Removed the /raw_query REST endpoint from --httpd. This will break very
      old clients that have not switched over the new streaming-based /query
      endoint or even newer /websocket.
  UI:
    * Changed detail panel to separate slice args from generic slice properties.
    * Automatically enabled sched_compact when generating trace configs for 
      Android S+ targets.
  SDK:
    * Added option for recording thread CPU times at the beginning and end of
      each slice.
    * Added perfetto::DynamicString() to use non-literal strings as event names
      in the TRACE_EVENT API.
    * Remove the pre-SDK consumer_api_deprecated interface. It was introduced
      for iorapd, now deleted from the Android tree.


v25.0 - 2022-04-01:
  Tracing service and probes:
    * Added prebuilts for mac-arm64.
    * Removed merged trace and config protos from Bazel. Embedder should
      instead depend on the non-merged proto targets.
    * Added FtraceConfig.disable_generic_events. If set, the ftrace data source
      will not emit events for which it doesn't have a compile-time proto
      message.
    * Added ingestion support for cros_ec (CrOS sensors) ftrace events.
    * Added ingestion support for kvm trace events.
    * Added reporting of atrace failures. Now they are bubbled up to the UI
      rather than causing atrace data to be silently missing.
  Trace Processor:
    * Added prebuilts for mac-arm64.
    * Changed LIKE comparisions to be case-insenstive. This reverts the change
      introduced in v22. GLOB should be used where case senstive searches are
      desired; built-in metrics continue to require the use of GLOB.
    * Added an optional dependency from trace processor onto a subset of
      sources from llvm-project for function name demangling. Bazel embedders
      might need to update their PERFETTO_CONFIG in perfetto_cfg.bzl to opt in
      or out of the new dependency. See
      perfetto/bazel/standalone/perfetto_cfg.bzl for details.
  UI:
    * Added flow arrows between binder transaction pairs (request/reply
      and async send/async recv).
  SDK:
    * Added support for writing typed proto messages inside DebugAnnotations.
    * Added support for delta encoding of timestamps for TrackEvents.
      To disable it, refer to `disable_incremental_timestamps` flag in
      `track_event_config.proto`.
  Tools:
    * Added support of gzip-compressed traces to traceconv.
    * Changed `traceconv text` to use an internal proto->pbtx converter rather
      than relying on libprotobuf. It could cause some small divergencies in the
      output format vs past releases.
    * Added tools/cpu_profile helper script to capture traces with callstack
      samples.


v24.2 - 2022-02-10:
  SDK:
    * Revert of incremental timestamps, introduced in v24.0.
      Some clients were depending on non-incremental timestamps.
      Future releases will re-enable this but offer an opt-out.


v24.1 - 2022-02-09:
  Tracing service and probes:
    * Fixed build failures on Windows.
  Trace Processor:
    * Fixed build failures on Windows.


v24.0 - 2022-02-08:
  Tracing service and probes:
    * Added "cpufreq_period_ms" in data source "linux.sys_stats" to poll
      /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq periodically.
    * Added support for Trusty TEE workqueue events.
    * Added support for more PMU events in traced_perf.
    * Changed output format of perfetto --query. Made the output more compact
      and added a summary of ongoing tracing sessions for the caller UID.
    * Changed timeout for traced stall detection from 2s to 4s.
    * Changed internal buffer management to split trace filtering in smaller
      tasks and avoid too large memory allocation when filtering.
    * Fixed a bug that could cause producers to see Flush() requests after an
      OnStop() and mis-behave if the tracing session is extremely short.
  Trace Processor:
    * Added support for passing multiple SQL statements to ExecuteQuery(). All
      queries will be executed fully, with the returned iterator yielding rows
      for the final statement.
    * Added support for multi-line SQL comments; previously only single line
      comments were supported.
  UI:
    * Added support for parsing instant events from legacy systrace formats.
    * Added ingestion and visualization for inet_sock_set_state and
      tcp_retransmit_skb events, showing TCP connections on dedicated tracks.
    * Changed HTTP+RPC to use the /websocket endpoint available in newer
      versions of trace_processor --httpd.
    * Changed text selection/copy: now allowed by default for DOM elements.
    * Changed search to also lookup slices by ID when the term is a number.
    * Changed postMessage() API, suppressed confirmation dialog when the opener
      is in the same origin, for cases when the UI is self-hosted.
  SDK:
    * Changed timestamps emitted by the SDK to be incremental by default, using
      ClockSnapshot + TracePacketDefaults.


v23.0 - 2022-01-11:
  Tracing service and probes:
    * Added workaround for a kernel ftrace bug causing some "comm" fields to be
      not null-terminated. https://github.com/torvalds/linux/commit/f0a5157803 .
    * Added ability to talk to the newer AIDL-based health hal in traced_probes.
      It still falls back on the older HIDL interface for older devices.
  Trace Processor:
    * Changed the argument for the trace path in constructor of TraceProcessor
      in the Python API from |file_path| to |trace|.
      |file_path| is deprecated and may be removed in the future.
    * Changed the Python API constructor. Now it takes a TraceProcessorConfig
      instead of passing parameters directly. This may break existing code
      but migration should be trivial (all current options are still
      supported).
    * Fixed a HTTP keepalive bug in trace_processor --httpd. The bug, introduced
      in v22.0, caused each RPC request to close the connection, effectively
      defeating the 'Connection: Keep-Alive', after each query made by the UI.
    * Added parsing of netif_receive_skb events from proto traces.
    * Added android_netperf metric based on netif events.
    * Fixed a bug that would cause fetch errors when loading traces > 32 MB when
      using trace_processor --httpd.
    * Added a workaround to tokenize properly /proc/pid/cmdline for chrome
      processes on Linux/CrOS. Chrome rewrites its cmdline replacing \0 -> ' '.
  UI:
    *
  SDK:
    *


v22.1 - 2021-12-07:
  Tracing service and probes:
    * Added workaround for a Linux kernel bug causing some ftrace strings to
      be non-null-terminated (https://github.com/torvalds/linux/commit/f0a5157).
  Trace Processor:
    * Fixed build failures on Windows.


v22.0 - 2021-12-03:
  Tracing service and probes:
    * Added Android SDK version to the SystemInfo trace packet.
    * Changed compiler flags. Assume recent x64 CPUs (-msse4.2 -mavx -mpopcnt).
      This behavior affects only standalone builds and can be changed by setting
      enable_perfetto_x64_cpu_opt=false in the GN args.
    * The java heap profiler now rescans all the processes every time for
      continous_dump_config. The scan_pids_only_on_start can be used to restore
      the old behavior.
    * Added support for building on ARM Macs.
    * Added support for the rss_stat_throttled event on Android via
      FtraceConfig.throttle_rss_stat. In newer Android kernels the base rss_stat
      event is now unthrottled. rss_stat used to be throttled by a downstream
      kernel change, unnecessary after https://lkml.org/lkml/2021/10/25/1411 .
      atrace.rc configures throttling from userspace at boot.
    * Fixed a bug that caused IPCs to stall traced and hit the watchdog if in
      the middle of a suspend/resume. Switched from SND_TIMEO to poll(POLLOUT).
    * Added "linux.sysfs_power" data source to poll /sys/class/power_supply/
      and report periodically battery charge and drain rate if supported.
    * Add snapshotting for non-BOOTTIME ftrace clocks. This fixes handling of
      ftrace events from old Linux kernel versions (i.e. 3.x) and adds
      proper support for using the "global" clock rather than "boot".
  Trace Processor:
    * Speeded up proto trace ingestion by 2x (~20 MB/s -> ~40 MB/s).
    * Changed LIKE comparisions to be case-senstive. This may break existing
      queries but was a necessary from a performance perspective.
      Going forward, GLOB must be used, instead of LIKE, for checked in metrics
      to avoid unnecessary slowdowns.
    * Changed compiler flags, assume recent x64 CPUs (see above).
    * Changed how displayTimeUnit is handled in JSON traces to match catapult.
    * Added websocket endpoint to RPC interface to reduce query latency.
    * Added support for hot-reloading metrics (see //docs/analysis/metrics.md).
    * Added ingestion support for non-BOOTTIME ftrace clocks.
  UI:
    * Added ability to save/restore record config. Remember last used config.
    * Fixed bug causing the recording page to hold onto the USB interface making
      adb unusable after a recording session.
  SDK:
    * Added UpdateDataSource() descriptor IPC endpoint to allow updates of the
      data source capabilities (e.g., category list for track event).


v21.0 - 2021-11-01:
  Tracing service and probes:
    * Added reporting of last 8 PERFETTO_LOG() entries and crash keys to
      crash tombstones on Android.
    * Changed kallsym parser to save 100ms for starting a tracing session with
      enable_ksyms=true.
    * Removed advertisement of the built-in data sources "android.heapprofd",
      "android.java_hprof", "linux.perf" on Linux and other platforms. Built-in
      data sources are only used to lazy-start daemons on Android OS.
    * Changed ACL files on Android atrace.rc to support to up to 24 ftrace cpus.
      No change on Linux which remains unlimited.
  Trace Processor:
    * Changed protobuf decoders to use less stack and fall back on heap sooner
      (before: 16KB of stack per decoder, after: 1.6KB). It caused problems with
      some embedders which use smaller per-thread stacks.
    * Added support for SPAN OUTER JOIN on unpartitioned tables.
    * Improved performance of as_pandas_dataframe() in the Python API by 16x.
  UI:
    * Added visualization of direct_reclaim ftrace events.
  SDK:
    * Added perfetto::{Flow,TerminatingFlow} to the track-event library.


v20.1 - 2021-10-05:
  Tracing service and probes:
    * Fixed standalone Windows build. Updated the llvm-win toolchain.


v20.0 - 2021-10-03:
  Tracing service and probes:
    * Removed DCHECK that would cause crashes when a debug build of the service
      is used with a producer built with -DNDEBUG.
    * Changed the service-side field-level filtering configuration protobuf
      field number, because the feature had a bug. This is effectively
      equivalent to deprecating the feature and reintroducing it under a
      different name.
    * Added support for boot tracing on Android. Early kernel tracing (prior to
      the point when /data is mounted) is not yet supported. For instructions
      see /docs/case-studies/android-boot-tracing.md .
  Trace Processor:
    * Added reqiurement of separating queries by semi-colon (;) followed by
      new-line when specifying a query file with -q to trace processor shell.
    * Added "ancestor_slice_by_stack" and "descendant_slice_by_stack" table
      functions to walk up and down the slice stacks.
    * Overhauled windowed sorting to be based on packet ordering and
      lifecycle events inside the trace instead of time-based ordering.
    * Removed |SortingMode::kForceFlushPeriodWindowedSort| due to changes to the
      sorting algorithm, which is now based on Flush events rather than time.
      Embedders should switch to |SortingMode::kDefaultHeuristics|. Other
      SortingMode enum values are no-ops and will be removed in future versions.
  UI:
    * Added initial flamegraph support for traced_perf callstack samples.
    * Added initial Pivot table for aggregation of userspace slices. The feature
      is disabled by default for and requires manual enabling via
      https://ui.perfetto.dev/#!/flags .
  SDK:
    * Changed DCHECK and DLOGs to be always disabled in SDK builds, regardless
      of NDEBUG.


v19.0 - 2021-09-02:
  Tracing service and probes:
    * Added ftrace clock reporting to the trace.
  Trace Processor:
    * Added support for longs/doubles to RUN_METRIC.
    * Added power profile data for sunfish, redfin, and bramble.
    * Added experimental Python library for computing slice breakdowns.
    * Fixed parsing of JSON escape sequences.
    * Fixed JSON trace detection.
  UI:
    * Added local cacheing of traces. Traces are reloaded in case of refresh or
      tab being discarded by the browser.
    * Added icon to distinguish metric-derived tracks.
    * Added release channel selector to feature flags page.
    * Fixed crash with null slice names.
  SDK:
    * Added some missing NESTABLE_ASYNC legacy trace macros.
    * Fixed reporting of producer uid in --query.
    * Fixed version numbering scheme for minor versions. Previously versions
      were numbered as like v19.0.42 where 42 represented the number of commits
      since the last major version release. This was ambiguous in the presence
      of branches. Now versions are numbered like v19.0-ab12cd34 where ab12cd34
      is the shortened Git commit-ish.


v18.0 - 2021-08-02:
  Tracing service and probes:
    * Added cross-compiler toolchains for Linux-{arm,64} based on Debian Sid.
      These will be used for generating monthly releases' prebuilts via LUCI.
  Trace Processor:
    * Added 'android_gpu' metric to report residency information for each GPU
      frequency (via `trace_processor_shell --run-metrics android_gpu`).
    * Removed the RawQuery RPC interface.
  UI:
    * Added a highlighted section to thread slices to visualize CPU time
      (darker) verses wall time (lighter).
    * Added global counter tracks for perf counters (e.g. "CPU 0 cycles", "CPU 0
      instructions") when the 'linux.perf' data source (traced_perf) is used.
    * Added a (feature) 'Flags' page to enable/disable individual metrics.
    * Fixed races that could cause occasional crashes when loading a trace
      from a permalink.
  SDK:
    * Fix undefined reference on ~TracingMuxerFake when building the SDK.


v17.0 - 2021-07-02:
  Tracing service and probes:
    * Fixed a bug in ftrace parsing of absolute timestamps
      (RINGBUF_TYPE_TIME_STAMP), encountered on Linux kernels 5.9+.
    * Fixed a bug in --save-for-bugreport causing 0-length traces if the
      selected trace declared one or more triggers in the config.
    * Fixed a bug in tracebox causing the PERFETTO_PRODUCER_SOCK_NAME env
      var to be ignored.
  Trace Processor:
    * Changed CORS headers of --httpd mode to allow only https://ui.perfetto.dev
      and http://localhost:10000. This affects only CORS-aware browser clients.
    * Added GPU frequency metrics.
  UI:
    * Fixed ADB connection issues ("unable to reset device") on Windows and Mac.
    * Added caching of tracing in the cache storage so that the trace is
      re-opened if a tab is killed (Chrome tab discarding or accidental CTRL+W).
  SDK:
    * Added support for writing track events using custom clock timestamps.


v16.1 - 2021-06-08:
  Tracing service and probes:
    * Cherry-pick of r.android.com/1716718 which missed the v16 branch cut and
      fixed MSVC 2019 builds.


v16.0 - 2021-06-01:
  Tracing service and probes:
    * Added support for building most targets (including traced, SDK and
      trace_processor_shell) from Windows using either clang-cl or MSVC 2019.
    * Added tracebox, a monolithic binary to capture traces with one command
      on Linux and older versions of Android (tested on Android Oreo).
    * Added support for service-side field-level filtering of traces. The
      consumer can pass a filter bytecode and ensure that non-allowed fields
      are never emitted in output.
    * Added reporting of service version and producer SDK version into the trace
      and `perfetto --query`.
    * Fixed compatibility with Android versions older than Pie (for sideloading)
      which cause failures when trying to enable atrace categories.
  Trace Processor:
    * Added new RPC interface based on a bidirectional binary pipe. This allows
      to simplify integration with out-of-process users. The existing --httpd
      interface now exposes a single /rpc endpoint. Older endpoints are still
      available for legacy clients.
    * Added support for counters and instant events in JSON traces.
    * Fixed support of displayTimeUnit in JSON traces.
  UI:
    * Added warning dialog when trying to use a trace_processor_shell --httpd
      which is too old.
    * Added warning dialog when trying to use a trace_processor_shell --httpd
      RPC instance from more than one tab.
    * Added links to convert the trace to JSON or systrace directly from the UI.
    * Changed track sorting logic. Tracks are now sorted in groups (e.g.,
      scheduling tracks, summary tracks, frame timeline tracks).
    * Fixed crashes happening flakily when pushing traces via window.open().


v15.0 - 2021-05-05:
  Tracing service and probes:
    * Added support for {host,target}=aarch64 standalone builds.
    * Added --background cmdline switch to traced and traced_probes services.
    * Changed trigger_perfetto to ignore unknown command line arguments to
      preserve forward compatibility.
    * Added -a / --app cmdline argument to tools/record_android_trace.
  Trace Processor:
    * Added sanitisation of keys in nested debug annotation dictionaries.
    * Changed Android startup metric: count CPU time of JIT thread pool, report
      timestamp of activities during startup.
    * Changed android_surfaceflinger metric, added missed frame counters.
    * Changed version of SQLite to 3.35.4.
    * Fixed importing of JSON traces with decimal (sub-us) timestamp.
    * Fixed prepending "debug." prefix to debug annotations with non-interned
      names.
  UI:
    * Added support to visualize the lifetime of individual dmabuf allocations
      as async slices (datasource: already existing ftrace dmabuf event).
    * Fixed visualization of unfinished slices to extend to the end of the
      viewport.
  SDK:
    * Added support for passing arbitrary number of debug annotations to
      TRACE_EVENT and combining them with lambdas.
    * Added support for writing typed TrackEvent arguments using TRACE_EVENT
      inline without lambdas.
    * Changed ConvertTimestampToTraceTimeNs to be a member of
      TraceTimestampTraits<T> struct instead of a standalone function.
    * Changed TracedValue to use nested DebugAnnotation proto instead of
      DebugAnnotation::NestedValue.


v14.0 - 2021-04-01:
  Tracing service and probes:
    * Added support for polling power rails on Android from the newer
      IPowerStats AIDL interface (previously using only the HAL interface).
    * Fixed native heap profiler crash when ABI of heapprofd and profiled
      process mismatch.
    * Changed encoding format of Anroid managed heap profiler to reduce heap
      dump sizes by delta-encoding object IDs.
  Trace Processor:
    * Added activity create/resume, layout inflation and resource timings to
      the Android startup metric.
    * Added chrome metadata key/value pairs (e.g. chrome version) into the
      `metadata` table with 'cr-' prefixed keys.
    * Added dma-buf-based memory metrics reporting total/avg/min/max dmabuf
      allocation per-dmabuf-heap and per-process.
    * Removed |force_full_sort| flag from config. This has been replaced
      by setting the sorting mode to force a full sort.
  UI:
    * Added tools/symbolize-ui-crash script to resolve crash reports via
      TypeScript source maps.
    * Fixed newlines when copying Android event log lines into the clipboard.
    * Fixed crash when selecting "Did not finish" slices.
    * Fixed OOM dialog to give actionable instructions when opening large traces
      rather than suggesting to file a bug.
  SDK:
    * Added /meson.build for bundling /sdk/perfetto.{cc,h} in Meson builds.
    * Added support for counter trace points with the TRACE_COUNTER macro.


v13.0 - 2021-03-01:
  Tracing service and probes:
    * Added ability to sample callstacks using kernel tracepoints as timebase.
    * Added abililty to record the perf timebase counter values into the trace,
      both combined callstack+counter or counter-only.
    * Added abillity to trigger traces based on VM pressure on Android. Requires
      a dedicated tracing instance in $tracefs/instances/mm_events.
  Trace Processor:
    * Added sorting mode to trace processor config to specify how trace
      processor should sort events. The |force_full_sort| flag has been
      deprecated (with replacement) and will be removed in the next version.
    * Added ingestion of frame timeline events into the
      {expected,actual}_frame_timeline_slice tables.
    * Added support for Mali's trace_marker_write ftrace event.
    * Added memory metric based on newer android_fastrpc kernel events.
  UI:
    * Added flow events support for instant events and async tracks.
    * Added support for Android frame timeline events. They allow inspecting
      end-to-end expected vs actual app-to-surfaceflinger frame times.
    * Added ability to switch between Canary and Stable channels in the UI.
    * Added ability to drag&drop to open trace files.
    * Changed UI serving infrastructure, old ui versions can be now retrieved by
      directly opening https://ui.perfetto.dev/v12.1.269/ .
    * Removed thread state track for threads that have no activity.
  SDK:
    * Use process start time hashed with the process id as a unique process
      identifier, allowing multiple independent users of the SDK in the same
      process to interleave their events on shared tracks.
    * Record process and thread names into the trace.
    * Add ring buffer tracing support, i.e., periodic clearing of incremental
      state.
  Misc:
    * Convert python scripts to python3.


v12.1 - 2021-02-01:
  Misc:
    * Fixed CHANGELOG which was missed in the 12.0 branch cut, causing
      mis-labeling of the version code in the v12.x branch as v11.0..N


v12.0 - 2021-02-01:
  Tracing service and probes:
    * Added more helpful error messages if the client library is used without
      having been initialized.
    * Added //tools/record_android_trace script to facilitate recording traces
      from Android devices, automating start + stop-via-ctrl+c + pull + open.
    * Added auto-attachment of traces to Android bugreports if dumpstate is
      invoked when a trace with bugreport_score > 0 is running.
  SDK:
    * Added ability to customize the timestamp of events via
      ConvertTimestampToTraceTimeNs().
    * Fixed support for category names that contain a space.
  Trace Processor:
    * Added ingestion and query support for Android end-to-end frame timing
      events through the {actual, expected}_frame_timeline_slice tables.
    * Added time-to-reportFullyDrawn (Android's API) to startup metrics.
    * Fixed excessive memory usage when decoding traces containing callstacks
      (https://github.com/google/perfetto/issues/83).
  UI:
    * Added ability to inspect the full trace config string from the
      'Info and stats' page.
    * Fixed 'TABLE/VIEW XXX already exists' in the Metrics page when running the
      same metric twice.
    * Fixed sorting of tracks using numeric sorting instead of lexicographic:
      Thread {1, 2, 10, 11, 20} rather than Thread {1, 10, 11, 2, 20}.
    * Fixed CSP-related bug that was preventing the UI to work on Firefox.
    * Changed max zoom resolution to allow to zoom to sub-us events.


v11.0 - 2021-01-01:
  Tracing service and probes:
    * Added trace packet interceptor API for rerouting trace data into
      non-Perfetto systems.
    * Added support for printing track events to the console.
    * Added a way to observe track event tracing sessions starting and
      stopping.
  Trace Processor:
    * Added "ancestor_slice" and "experimental_ancestor_stack_profile_callsite"
      table functions to look up ancestors of CPU stack samples in profiler
      tables.
    * Added power metric reporting suspend/resume time periods.
  UI:
    * Fixed CPU time calculation in example queries.
    * Added tracks to debug Android SystemUI jank.


v10.0 - 2020-12-01:
  Tracing service and probes:
    * Fixed crash of tracing service if a client is unresponsive on the IPC
      channel. Clients are disconnected if they don't respond to IPCs for 10s.
    * Added cmdline arguments for integration within ChromeOS system image
      (--{producer,consumer}-socket-{group,mode} for chmod-ing sockets).
    * Changed path lookup logic for traced socket. /run/perfetto/ is used if the
      directory exists, falling back on /tmp/ otherwise.
    * Added support for kernel frame symbolization to the traced_perf callstack
      sampler.
    * Added support for resolving ftrace event arguments that require
      symbolization against printk_format.
  Trace Processor:
    * Added .read command to inject a SQL query file, similar to the -q cmdline.
    * Added trace-based metrics to root cause jank in Android System UI.
    * Added symbolization support for ELF files on Windows for heap and
      callstack profilers.
    * Added support for symbolizing names of workqueue ftrace events.
    * Improved Android startup metric with activity restart time.
  UI:
    * Added support for navigating flows with Ctrl+[ / Ctr+].
    * Improved query result panel, moved to the bottom group allowing
      simultaneous query result and timeline views.
    * Fixed data corruption when recording traces via the WebUSB-based Record
      page in the UI.


v9.0 - 2020-11-01:
  Tracing service and probes:
    * Added support for recording traces from a system service through the
      client API.
    * The client library now reconnects producers automatically if the
      connection to the tracing service is lost. Also fixed crashes in ongoing
      tracing sessions when a disconnect occurs.
    * Added support for dpu and g2d ftrace events.
    * Enabled commit batching and producer side patching of chunks.
    * Add support for symbolizing kernel symbols for ftrace events.
  Trace Processor:
    * Fixed type affinity of string columns.
  UI:
    * Added initial support for running metrics from the UI.
    * Added support for displaying all flows when a slice or area is selected.
    * Highlight nodes that match the 'focus' string in the flamegraph.
    * Added search within slice args.
    * Fixed details panel height and moved query panel into details panel.
    * Enabled re-sharing of postMessage traces by echoing back the original URL.
    * Improved record page error messages.


v8.0 - 2020-10-01:
  Tracing service and probes:
    * Added API for querying registered data sources and their capabilities.
    * Added support for profiling heap allocations on Linux via LD_PRELOAD.
    * Fixed possible race when initializing the consumer library.
    * Fixed subtle bugs on systems with 16KB system pages.
  Trace Processor:
    * Added a table which lists available metrics.
    * Added Python bindings on PyPi in the 'perfetto' package.
    * Added support for running trace_processor_shell on Android.
    * Added per-process metrics for GPU memory usage.
    * Added support for exporting flow events to JSON.
    * Added dynamic tables for navigating between slices of flows.
  UI:
    * Changed time marking: horizontal selection doesn't gray out anymore,
      pressing 'm' marks the range.
    * Added initial support for displaying flow event arrows.
    * Improved ordering of all thread tracks under process grouping.
    * Fixed UI crashes due to metric errors
    * Fixed selection of thread state slices.


v7.0 - 2020-09-01:
  Tracing service and probes:
    * Added auto-reconnection to the SDK. Tracing::Initialize() now retries in
      the background, instead of failing, if the tracing service is unrechable.
    * Added support for recording cpuhp (CPU hotplug) ftrace events.
    * Fixed heap profiling unwinding on multi-ABI systems.
    * Fixed reporting of live objects in the native heap profiler when using
      --dump-at-max.
    * Fixed crash when writing trace events with field nesting level > 10.
  Trace Processor:
    * Added Python bindings, see
      https://perfetto.dev/docs/analysis/trace-processor#python-api .
    * Added ingestion for Chrome instant events and Chrome flow events.
    * Added ingestion for Android GPU memory events and sched_blocked_reason.
    * Added WebView power metric.
    * Added support for WSL1 where Async I/O is not available.
    * Improved detection of Android suspend/resume events.
  UI:
    * Added GPU memory recording controls and ingestion code. Requires a recent
      Android 12+ kernel.
    * Added details panel for flow events, showed when the user selects a slice
      involved in a flow (arrows in the UI are still being worked on).
    * Added instant events rendering.
    * Added Google Analytics.
    * Fixed I/O thread-states in 4.14 kernels to deal with the removal of
      wake-kill using sched_blocked_reason.
    * Fixed "Perfetto UI started debugging this browser" showing when opening
      the UI and the Chrome extension is installed.
  Misc:
    * Update language to comply with Android's inclusive language guidance.


v6.0 - 2020-08-01:
  Tracing service and probes:
    * Added ftrace thermal events.
    * Added support for custom allocators to the heap profiler. Allows
      developers to report memory allocations that are not done through malloc.
    * Added detailed timestamping of key tracing session events.
    * Added support for building tracing services on CrOS (system-wide tracing).
    * Fixed filtering out of stale ftrace data that predates the beginning of
      the tracing session.
  Trace Processor:
    * Improved profile symbolizer. PERFETTO_SYMBOLIZER_MODE=index discovers
      symbol files by build id rather than name.
    * Added screen-state Android metrics.
  UI:
    * Added 'Info and stats' page to debug data losses and trace stats.
    * Added full cmdline to process detail panel.
    * Improved performance of async tracks using quantized queries.
    * Improved performance of counter and slice tracks for long traces by
      pre-caching quantized track data.
    * Improved actionablility of crash dialog when the Wasm module OOMs.


v5.0 - 2020-07-01:
  Tracing service and probes:
    * Added gpu_mem_total ftrace event.
    * Added TrustZone (scm start/end) event.
    * Added protos for GPU memory tracking and updated render stages proto.
    * Added time_in_state probe for Android (CPU time broken down by frequency).

  Trace Processor:
    * Added ingestion of IRQ and SoftIRQ events.
    * Added ingestion of workqueue events. KAddr symbolization still missing.
    * Added ingestion of voltage regulators and board clock change events.
    * Added ingestion of new ION ion_buffer_create/destroy events.
    * Added ingestion of TrustZone (scm start/end) events.
    * Added SurfaceFlinger derived events (tracking of missed frames).
    * Changed parsing of scheduler task state on 4.14 kernels.
    * Changed importing of Java heap graphs: allow partial dumps.
    * Improved performance of the SQL query engine.

  UI:
    * Added dedicated query page for custom SQL queries.
    * Added navigation links for Binder slices.
    * Removed overview summary mode when zoomed out.
    * Fixed recording page when targeting Android P.
    * Improved slice pan/zoom performance by quantizing.