mirror of
https://github.com/python/cpython.git
synced 2025-10-31 13:41:24 +00:00
be0c106789
Co-authored-by: Aniket Panse <aniketpanse@fb.com> Co-authored-by: Gregory P. Smith <greg@krypto.org> Co-authored-by: Carl Meyer <carl@oddbird.net>
50 lines
2.3 KiB
ReStructuredText
50 lines
2.3 KiB
ReStructuredText
.. highlight:: c
|
|
|
|
.. _perfmaps:
|
|
|
|
Support for Perf Maps
|
|
----------------------
|
|
|
|
On supported platforms (as of this writing, only Linux), the runtime can take
|
|
advantage of *perf map files* to make Python functions visible to an external
|
|
profiling tool (such as `perf <https://perf.wiki.kernel.org/index.php/Main_Page>`_).
|
|
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 <https://git.kernel.org/pub/scm/linux/
|
|
kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt>`_.
|
|
|
|
In Python, these helper APIs can be used by libraries and features that rely
|
|
on generating machine code on the fly.
|
|
|
|
Note that holding the Global Interpreter Lock (GIL) 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.
|