On supported platforms (Linux and macOS), the runtime can take
advantage of perf map files to make Python functions visible to an external
profiling tool (such as perf or
samply). A running process may create a
file in the /tmp directory, which contains entries that can map a section
of executable code to a name. This interface is described in the
documentation of the Linux Perf tool.
In Python, these helper APIs can be used by libraries and features that rely on generating machine code on the fly.
Note that holding an :term:`attached thread state` is not required for these APIs.
.. c:function:: int PyUnstable_PerfMapState_Init(void)
Open the ``/tmp/perf-$pid.map`` file, unless it's already opened, and create
a lock to ensure thread-safe writes to the file (provided the writes are
done through :c:func:`PyUnstable_WritePerfMapEntry`). Normally, there's no need
to call this explicitly; just use :c:func:`PyUnstable_WritePerfMapEntry`
and it will initialize the state on first call.
Returns ``0`` on success, ``-1`` on failure to create/open the perf map file,
or ``-2`` on failure to create a lock. Check ``errno`` for more information
about the cause of a failure... c:function:: int PyUnstable_WritePerfMapEntry(const void *code_addr, unsigned int code_size, const char *entry_name)
Write one single entry to the ``/tmp/perf-$pid.map`` file. This function is
thread safe. Here is what an example entry looks like::
# address size name
7f3529fcf759 b py::bar:/run/t.py
Will call :c:func:`PyUnstable_PerfMapState_Init` before writing the entry, if
the perf map file is not already opened. Returns ``0`` on success, or the
same error codes as :c:func:`PyUnstable_PerfMapState_Init` on failure... c:function:: void PyUnstable_PerfMapState_Fini(void)
Close the perf map file opened by :c:func:`PyUnstable_PerfMapState_Init`.
This is called by the runtime itself during interpreter shut-down. In
general, there shouldn't be a reason to explicitly call this, except to
handle specific scenarios such as forking.These unstable functions let you access and set perf map information about the current frame from C code.
Note: Appends the content of the parent frame to the current one in perf maps. Just like in frameobject.h.
.. c:function:: int PyUnstable_CopyPerfMapFile(const char *parent_filename)
Open the ``/tmp/perf-$pid.map`` file and append the content of *parent_filename*
to it.
This function is only available on platforms that support perf maps (currently
Linux). Return ``0`` on success, ``-1`` on failure.
.. versionadded:: 3.13
.. c:function:: int PyUnstable_PerfTrampoline_CompileCode(PyCodeObject *code)
Compile the given code object using the current perf trampoline.
The "current" trampoline is the one set by the runtime or the most recent
:c:func:`PyUnstable_PerfTrampoline_SetPersistAfterFork` call.
If no trampoline is set, falls back to normal compilation (no perf map entry).
:param code: The code object to compile.
:return: 0 on success, -1 on failure.
.. versionadded:: 3.13
.. c:function:: int PyUnstable_PerfTrampoline_SetPersistAfterFork(int enable)
Set whether the perf trampoline should persist after a fork.
* If ``enable`` is true (non-zero): perf map file remains open/valid post-fork.
Child process inherits all existing perf map entries.
* If ``enable`` is false (zero): perf map closes post-fork.
Child process gets empty perf map.
Default: false (clears on fork).
:param enable: 1 to enable, 0 to disable.
:return: 0 on success, -1 on failure.
.. versionadded:: 3.13