gh-138122: Make the tachyon profiler opcode-aware (#142394)

Author: pablogsal

Doc/library/profiling.sampling.rst

@@ -13,6 +13,8 @@
 
 **Source code:** :source:`Lib/profiling/sampling/`
 
+.. program:: profiling.sampling
+
 --------------
 
 .. image:: tachyon-logo.png
@@ -146,6 +148,10 @@ Generate a line-by-line heatmap::
 
    python -m profiling.sampling run --heatmap script.py
 
+Enable opcode-level profiling to see which bytecode instructions are executing::
+
+   python -m profiling.sampling run --opcodes --flamegraph script.py
+
 
 Commands
 ========
@@ -308,7 +314,7 @@ The two most fundamental parameters are the sampling interval and duration.
 Together, these determine how many samples will be collected during a profiling
 session.
 
-The ``--interval`` option (``-i``) sets the time between samples in
+The :option:`--interval` option (:option:`-i`) sets the time between samples in
 microseconds. The default is 100 microseconds, which produces approximately
 10,000 samples per second::
 
@@ -319,7 +325,7 @@ cost of slightly higher profiler CPU usage. Higher intervals reduce profiler
 overhead but may miss short-lived functions. For most applications, the
 default interval provides a good balance between accuracy and overhead.
 
-The ``--duration`` option (``-d``) sets how long to profile in seconds. The
+The :option:`--duration` option (:option:`-d`) sets how long to profile in seconds. The
 default is 10 seconds::
 
    python -m profiling.sampling run -d 60 script.py
@@ -337,8 +343,8 @@ Python programs often use multiple threads, whether explicitly through the
 :mod:`threading` module or implicitly through libraries that manage thread
 pools.
 
-By default, the profiler samples only the main thread. The ``--all-threads``
-option (``-a``) enables sampling of all threads in the process::
+By default, the profiler samples only the main thread. The :option:`--all-threads`
+option (:option:`-a`) enables sampling of all threads in the process::
 
    python -m profiling.sampling run -a script.py
 
@@ -357,7 +363,7 @@ additional context about what the interpreter is doing at the moment each
 sample is taken. These synthetic frames help distinguish different types of
 execution that would otherwise be invisible.
 
-The ``--native`` option adds ``<native>`` frames to indicate when Python has
+The :option:`--native` option adds ``<native>`` frames to indicate when Python has
 called into C code (extension modules, built-in functions, or the interpreter
 itself)::
 
@@ -369,7 +375,7 @@ in the Python function that made the call. This is useful when optimizing
 code that makes heavy use of C extensions like NumPy or database drivers.
 
 By default, the profiler includes ``<GC>`` frames when garbage collection is
-active. The ``--no-gc`` option suppresses these frames::
+active. The :option:`--no-gc` option suppresses these frames::
 
    python -m profiling.sampling run --no-gc script.py
 
@@ -379,10 +385,48 @@ see substantial time in ``<GC>`` frames, consider investigating object
 allocation rates or using object pooling.
 
 
+Opcode-aware profiling
+----------------------
+
+The :option:`--opcodes` option enables instruction-level profiling that captures
+which Python bytecode instructions are executing at each sample::
+
+   python -m profiling.sampling run --opcodes --flamegraph script.py
+
+This feature provides visibility into Python's bytecode execution, including
+adaptive specialization optimizations. When a generic instruction like
+``LOAD_ATTR`` is specialized at runtime into a more efficient variant like
+``LOAD_ATTR_INSTANCE_VALUE``, the profiler shows both the specialized name
+and the base instruction.
+
+Opcode information appears in several output formats:
+
+- **Live mode**: An opcode panel shows instruction-level statistics for the
+  selected function, accessible via keyboard navigation
+- **Flame graphs**: Nodes display opcode information when available, helping
+  identify which instructions consume the most time
+- **Heatmap**: Expandable bytecode panels per source line show instruction
+  breakdown with specialization percentages
+- **Gecko format**: Opcode transitions are emitted as interval markers in the
+  Firefox Profiler timeline
+
+This level of detail is particularly useful for:
+
+- Understanding the performance impact of Python's adaptive specialization
+- Identifying hot bytecode instructions that might benefit from optimization
+- Analyzing the effectiveness of different code patterns at the instruction level
+- Debugging performance issues that occur at the bytecode level
+
+The :option:`--opcodes` option is compatible with :option:`--live`, :option:`--flamegraph`,
+:option:`--heatmap`, and :option:`--gecko` formats. It requires additional memory to store
+opcode information and may slightly reduce sampling performance, but provides
+unprecedented visibility into Python's execution model.
+
+
 Real-time statistics
 --------------------
 
-The ``--realtime-stats`` option displays sampling rate statistics during
+The :option:`--realtime-stats` option displays sampling rate statistics during
 profiling::
 
    python -m profiling.sampling run --realtime-stats script.py
@@ -434,7 +478,7 @@ CPU execution time, or time spent holding the global interpreter lock.
 Wall-clock mode
 ---------------
 
-Wall-clock mode (``--mode=wall``) captures all samples regardless of what the
+Wall-clock mode (:option:`--mode`\ ``=wall``) captures all samples regardless of what the
 thread is doing. This is the default mode and provides a complete picture of
 where time passes during program execution::
 
@@ -454,7 +498,7 @@ latency.
 CPU mode
 --------
 
-CPU mode (``--mode=cpu``) records samples only when the thread is actually
+CPU mode (:option:`--mode`\ ``=cpu``) records samples only when the thread is actually
 executing on a CPU core::
 
    python -m profiling.sampling run --mode=cpu script.py
@@ -488,7 +532,7 @@ connection pooling, or reducing wait time instead.
 GIL mode
 --------
 
-GIL mode (``--mode=gil``) records samples only when the thread holds Python's
+GIL mode (:option:`--mode`\ ``=gil``) records samples only when the thread holds Python's
 global interpreter lock::
 
    python -m profiling.sampling run --mode=gil script.py
@@ -520,7 +564,7 @@ output goes to stdout, a file, or a directory depending on the format.
 pstats format
 -------------
 
-The pstats format (``--pstats``) produces a text table similar to what
+The pstats format (:option:`--pstats`) produces a text table similar to what
 deterministic profilers generate. This is the default output format::
 
    python -m profiling.sampling run script.py
@@ -567,31 +611,31 @@ interesting functions that highlights:
   samples (high cumulative/direct multiplier). These are frequently-nested
   functions that appear deep in many call chains.
 
-Use ``--no-summary`` to suppress both the legend and summary sections.
+Use :option:`--no-summary` to suppress both the legend and summary sections.
 
 To save pstats output to a file instead of stdout::
 
    python -m profiling.sampling run -o profile.txt script.py
 
 The pstats format supports several options for controlling the display.
-The ``--sort`` option determines the column used for ordering results::
+The :option:`--sort` option determines the column used for ordering results::
 
    python -m profiling.sampling run --sort=tottime script.py
    python -m profiling.sampling run --sort=cumtime script.py
    python -m profiling.sampling run --sort=nsamples script.py
 
-The ``--limit`` option restricts output to the top N entries::
+The :option:`--limit` option restricts output to the top N entries::
 
    python -m profiling.sampling run --limit=30 script.py
 
-The ``--no-summary`` option suppresses the header summary that precedes the
+The :option:`--no-summary` option suppresses the header summary that precedes the
 statistics table.
 
 
 Collapsed stacks format
 -----------------------
 
-Collapsed stacks format (``--collapsed``) produces one line per unique call
+Collapsed stacks format (:option:`--collapsed`) produces one line per unique call
 stack, with a count of how many times that stack was sampled::
 
    python -m profiling.sampling run --collapsed script.py
@@ -621,7 +665,7 @@ visualization where you can click to zoom into specific call paths.
 Flame graph format
 ------------------
 
-Flame graph format (``--flamegraph``) produces a self-contained HTML file with
+Flame graph format (:option:`--flamegraph`) produces a self-contained HTML file with
 an interactive flame graph visualization::
 
    python -m profiling.sampling run --flamegraph script.py
@@ -667,7 +711,7 @@ or through their callees.
 Gecko format
 ------------
 
-Gecko format (``--gecko``) produces JSON output compatible with the Firefox
+Gecko format (:option:`--gecko`) produces JSON output compatible with the Firefox
 Profiler::
 
    python -m profiling.sampling run --gecko script.py
@@ -694,14 +738,14 @@ Firefox Profiler timeline:
 - **Code type markers**: distinguish Python code from native (C extension) code
 - **GC markers**: indicate garbage collection activity
 
-For this reason, the ``--mode`` option is not available with Gecko format;
+For this reason, the :option:`--mode` option is not available with Gecko format;
 all relevant data is captured automatically.
 
 
 Heatmap format
 --------------
 
-Heatmap format (``--heatmap``) generates an interactive HTML visualization
+Heatmap format (:option:`--heatmap`) generates an interactive HTML visualization
 showing sample counts at the source line level::
 
    python -m profiling.sampling run --heatmap script.py
@@ -744,7 +788,7 @@ interpretation of hierarchical visualizations.
 Live mode
 =========
 
-Live mode (``--live``) provides a terminal-based real-time view of profiling
+Live mode (:option:`--live`) provides a terminal-based real-time view of profiling
 data, similar to the ``top`` command for system processes::
 
    python -m profiling.sampling run --live script.py
@@ -760,6 +804,11 @@ and thread status statistics (GIL held percentage, CPU usage, GC time). The
 main table shows function statistics with the currently sorted column indicated
 by an arrow (▼).
 
+When :option:`--opcodes` is enabled, an additional opcode panel appears below the
+main table, showing instruction-level statistics for the currently selected
+function. This panel displays which bytecode instructions are executing most
+frequently, including specialized variants and their base opcodes.
+
 
 Keyboard commands
 -----------------
@@ -813,20 +862,25 @@ Within live mode, keyboard commands control the display:
 :kbd:`h` or :kbd:`?`
    Show the help screen with all available commands.
 
+:kbd:`j` / :kbd:`k` (or :kbd:`Up` / :kbd:`Down`)
+   Navigate through opcode entries in the opcode panel (when ``--opcodes`` is
+   enabled). These keys scroll through the instruction-level statistics for the
+   currently selected function.
+
 When profiling finishes (duration expires or target process exits), the display
 shows a "PROFILING COMPLETE" banner and freezes the final results. You can
 still navigate, sort, and filter the results before pressing :kbd:`q` to exit.
 
-Live mode is incompatible with output format options (``--collapsed``,
-``--flamegraph``, and so on) because it uses an interactive terminal
+Live mode is incompatible with output format options (:option:`--collapsed`,
+:option:`--flamegraph`, and so on) because it uses an interactive terminal
 interface rather than producing file output.
 
 
 Async-aware profiling
 =====================
 
 For programs using :mod:`asyncio`, the profiler offers async-aware mode
-(``--async-aware``) that reconstructs call stacks based on the task structure
+(:option:`--async-aware`) that reconstructs call stacks based on the task structure
 rather than the raw Python frames::
 
    python -m profiling.sampling run --async-aware async_script.py
@@ -846,16 +900,16 @@ and presenting stacks that reflect the ``await`` chain.
 Async modes
 -----------
 
-The ``--async-mode`` option controls which tasks appear in the profile::
+The :option:`--async-mode` option controls which tasks appear in the profile::
 
    python -m profiling.sampling run --async-aware --async-mode=running async_script.py
    python -m profiling.sampling run --async-aware --async-mode=all async_script.py
 
-With ``--async-mode=running`` (the default), only the task currently executing
+With :option:`--async-mode`\ ``=running`` (the default), only the task currently executing
 on the CPU is profiled. This shows where your program is actively spending time
 and is the typical choice for performance analysis.
 
-With ``--async-mode=all``, tasks that are suspended (awaiting I/O, locks, or
+With :option:`--async-mode`\ ``=all``, tasks that are suspended (awaiting I/O, locks, or
 other tasks) are also included. This mode is useful for understanding what your
 program is waiting on, but produces larger profiles since every suspended task
 appears in each sample.
@@ -884,8 +938,8 @@ Option restrictions
 -------------------
 
 Async-aware mode uses a different stack reconstruction mechanism and is
-incompatible with: ``--native``, ``--no-gc``, ``--all-threads``, and
-``--mode=cpu`` or ``--mode=gil``.
+incompatible with: :option:`--native`, :option:`--no-gc`, :option:`--all-threads`, and
+:option:`--mode`\ ``=cpu`` or :option:`--mode`\ ``=gil``.
 
 
 Command-line interface
@@ -939,6 +993,13 @@ Sampling options
 
    Enable async-aware profiling for asyncio programs.
 
+.. option:: --opcodes
+
+   Gather bytecode opcode information for instruction-level profiling. Shows
+   which bytecode instructions are executing, including specializations.
+   Compatible with ``--live``, ``--flamegraph``, ``--heatmap``, and ``--gecko``
+   formats only.
+
 
 Mode options
 ------------