Skip to content

gh-141004: Document unstable perf map functions in ceval.h #143492

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Yashp002 wants to merge 7 commits into
base: main
Choose a base branch
from
+40 −4
Open

gh-141004: Document unstable perf map functions in ceval.h #143492

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
9a85c56
first commit perfmaps
Yashp002 Jan 6, 2026
5e050f1
fix 1 perfmaps
Yashp002 Jan 6, 2026
bd7eb99
fix 2 perfmaps
Yashp002 Jan 8, 2026
e5a2111
perfmaps fix 3
Yashp002 Jan 31, 2026
a7a9e53
Merge branch 'main' into doc-ceval-perf
Yashp002 Jan 31, 2026
85b98cf
fix capi_ignored
Yashp002 Jan 31, 2026
5c89eea
perfmaps fix 4
Yashp002 Feb 2, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 40 additions & 0 deletions Doc/c-api/perfmaps.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -49,3 +49,43 @@ Note that holding an :term:`attached thread state` is not required for these API
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.

.. c:function:: int PyUnstable_CopyPerfMapFile(const char *parent_filename)

Open the ``/tmp/perf-$pid.map`` file and append the content of *parent_filename*
Copy link
Member

@StanFromIreland StanFromIreland Jan 6, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This should note what happens on Windows where this obviously won't work.

Copy link
Member

@encukou encukou Jan 7, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

That's the case for all of these functions; the info should be in the beginning of the section.

This doesn't open the perf map file directly; it should use the same wording as PyUnstable_WritePerfMapEntry: “Will call :c:func:PyUnstable_PerfMapState_Init…”

Copy link
Contributor Author

@Yashp002 Yashp002 Jan 7, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@encukou Would this wording be suitable then as a replacement for line 56 as:

"Calls :c:func:PyUnstable_PerfMapState_Init if the perf map is not yet
initialized, then append the content of parent_filename to the perf map."

Copy link
Contributor Author

@Yashp002 Yashp002 Jan 8, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@encukou or @StanFromIreland Could you verify this one too?

Copy link
Member

@encukou encukou Jan 8, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'd say only “Append contents of the file named parent_filename to the perf map.” in the opening paragraph, and add the note about _Init later (like in WritePerfMapEntry docs).

to it.

This function is available on all platforms but only generates output on platforms
that support perf maps (currently only Linux). On other platforms, it does nothing.

.. 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
4 changes: 0 additions & 4 deletions Tools/check-c-api-docs/ignored_c_api.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,10 +71,6 @@ PyDescr_TYPE
PyWrapperFlag_KEYWORDS
# cpython/fileobject.h
Py_UniversalNewlineFgets
# cpython/ceval.h
PyUnstable_CopyPerfMapFile
PyUnstable_PerfTrampoline_CompileCode
PyUnstable_PerfTrampoline_SetPersistAfterFork
# cpython/pyframe.h
PyUnstable_EXECUTABLE_KINDS
PyUnstable_EXECUTABLE_KIND_BUILTIN_FUNCTION
Expand Down
Loading