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GH-123299: Copyedit 3.14 What's New: Optimizations (#137789)
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Adam Turner
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2 changed files with 106 additions and 81 deletions
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@ -75,6 +75,7 @@ The debugger's prompt is ``(Pdb)``, which is the indicator that you are in debug
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arguments of the ``p`` command.
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.. _pdb-cli:
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.. program:: pdb
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You can also invoke :mod:`pdb` from the command line to debug other scripts. For
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@ -1288,12 +1288,11 @@ asyncio
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:meth:`asyncio.TaskGroup.create_task`.
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(Contributed by Thomas Grainger in :gh:`128307`.)
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bdb
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---
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* The :mod:`bdb` module now supports the :mod:`sys.monitoring` backend.
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(Contributed by Tian Gao in :gh:`124533`.)
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* There are two new utility functions for
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introspecting and printing a program's call graph:
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:func:`~asyncio.capture_call_graph` and :func:`~asyncio.print_call_graph`.
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(Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
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in :gh:`91048`.)
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.. _whatsnew314-color-calendar:
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@ -1521,36 +1520,6 @@ functools
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(Contributed by Sayandip Dutta in :gh:`125916`.)
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gc
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--
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The cyclic garbage collector is now incremental,
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which changes the meaning of the results of
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:meth:`~gc.get_threshold` and :meth:`~gc.set_threshold`
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as well as :meth:`~gc.get_count` and :meth:`~gc.get_stats`.
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* For backwards compatibility, :meth:`~gc.get_threshold` continues to return
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a three-item tuple.
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The first value is the threshold for young collections, as before;
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the second value determines the rate at which the old collection is scanned
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(the default is 10, and higher values mean that the old collection
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is scanned more slowly).
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The third value is meaningless and is always zero.
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* :meth:`~gc.set_threshold` ignores any items after the second.
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* :meth:`~gc.get_count` and :meth:`~gc.get_stats` continue to return
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the same format of results.
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The only difference is that instead of the results referring to
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the young, aging and old generations,
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the results refer to the young generation
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and the aging and collecting spaces of the old generation.
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In summary, code that attempted to manipulate the behavior of the cycle GC
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may not work exactly as intended, but it is very unlikely to be harmful.
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All other code will work just fine.
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getopt
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------
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@ -1919,13 +1888,6 @@ pdb
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* ``$_asynctask`` is added to access the current asyncio task if applicable.
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(Contributed by Tian Gao in :gh:`124367`.)
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* :mod:`pdb` now supports two backends: :func:`sys.settrace` and
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:mod:`sys.monitoring`. Using :mod:`pdb` CLI or :func:`breakpoint` will
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always use the :mod:`sys.monitoring` backend. Explicitly instantiating
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:class:`pdb.Pdb` and its derived classes will use the :func:`sys.settrace`
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backend by default, which is configurable.
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(Contributed by Tian Gao in :gh:`124533`.)
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* :func:`pdb.set_trace_async` is added to support debugging asyncio
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coroutines. :keyword:`await` statements are supported with this
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function.
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@ -2266,14 +2228,16 @@ zipinfo
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.. Add improved modules above alphabetically, not here at the end.
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Optimizations
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=============
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* The import time for several standard library modules has been improved,
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including :mod:`ast`, :mod:`asyncio`, :mod:`base64`, :mod:`cmd`, :mod:`csv`,
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:mod:`gettext`, :mod:`importlib.util`, :mod:`locale`, :mod:`mimetypes`,
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:mod:`optparse`, :mod:`pickle`, :mod:`pprint`, :mod:`pstats`, :mod:`socket`,
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:mod:`subprocess`, :mod:`threading`, :mod:`tomllib`, and :mod:`zipfile`.
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including :mod:`annotationlib`, :mod:`ast`, :mod:`asyncio`, :mod:`base64`,
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:mod:`cmd`, :mod:`csv`, :mod:`gettext`, :mod:`importlib.util`, :mod:`locale`,
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:mod:`mimetypes`, :mod:`optparse`, :mod:`pickle`, :mod:`pprint`,
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:mod:`pstats`, :mod:`shlex`, :mod:`socket`, :mod:`string`, :mod:`subprocess`,
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:mod:`threading`, :mod:`tomllib`, :mod:`types`, and :mod:`zipfile`.
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(Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz,
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Hugo van Kemenade, Jelle Zijlstra, and others in :gh:`118761`.)
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@ -2282,32 +2246,44 @@ Optimizations
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asyncio
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-------
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* :mod:`asyncio` has a new per-thread double linked list implementation internally for
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:class:`native tasks <asyncio.Task>` which speeds up execution by 10-20% on standard
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pyperformance benchmarks and reduces memory usage.
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* Standard benchmark results have improved by 10-20%, following the
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implementation of a new per-thread double linked list
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for :class:`native tasks <asyncio.Task>`,
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also reducing memory usage.
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This enables external introspection tools such as
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:ref:`python -m asyncio pstree <whatsnew314-asyncio-introspection>`
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to introspect the call graph of asyncio tasks running in all threads.
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(Contributed by Kumar Aditya in :gh:`107803`.)
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* :mod:`asyncio` has first class support for :term:`free-threading builds <free threading>`.
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This enables parallel execution of multiple event loops across different threads and scales
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linearly with the number of threads.
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* The module now has first class support for
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:term:`free-threading builds <free threading>`.
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This enables parallel execution of multiple event loops across
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different threads, scaling linearly with the number of threads.
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(Contributed by Kumar Aditya in :gh:`128002`.)
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* :mod:`asyncio` has new utility functions for introspecting and printing
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the program's call graph: :func:`asyncio.capture_call_graph` and
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:func:`asyncio.print_call_graph`.
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(Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
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in :gh:`91048`.)
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base64
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------
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* Improve the performance of :func:`base64.b16decode` by up to ten times,
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and reduce the import time of :mod:`base64` by up to six times.
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(Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in :gh:`118761`.)
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* :func:`~base64.b16decode` is now up to six times faster.
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(Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner
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in :gh:`118761`.)
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bdb
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---
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* The basic debugger now has a :mod:`sys.monitoring`-based backend,
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which can be selected via the passing ``'monitoring'``
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to the :class:`~bdb.Bdb` class's new *backend* parameter.
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(Contributed by Tian Gao in :gh:`124533`.)
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difflib
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-------
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* The :func:`~difflib.IS_LINE_JUNK` function is now up to twice as fast.
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(Contributed by Adam Turner and Semyon Moroz in :gh:`130167`.)
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gc
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@ -2316,42 +2292,90 @@ gc
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* The new :ref:`incremental garbage collector <whatsnew314-incremental-gc>`
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means that maximum pause times are reduced
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by an order of magnitude or more for larger heaps.
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Because of this optimization, the meaning of the results of
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:meth:`~gc.get_threshold` and :meth:`~gc.set_threshold` have changed,
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along with :meth:`~gc.get_count` and :meth:`~gc.get_stats`.
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- For backwards compatibility, :meth:`~gc.get_threshold` continues to return
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a three-item tuple.
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The first value is the threshold for young collections, as before;
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the second value determines the rate at which the old collection is scanned
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(the default is 10, and higher values mean that the old collection
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is scanned more slowly).
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The third value is now meaningless and is always zero.
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- :meth:`~gc.set_threshold` now ignores any items after the second.
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- :meth:`~gc.get_count` and :meth:`~gc.get_stats` continue to return
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the same format of results.
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The only difference is that instead of the results referring to
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the young, aging and old generations,
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the results refer to the young generation
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and the aging and collecting spaces of the old generation.
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In summary, code that attempted to manipulate the behavior of the cycle GC
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may not work exactly as intended, but it is very unlikely to be harmful.
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All other code will work just fine.
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(Contributed by Mark Shannon in :gh:`108362`.)
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io
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---
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* :mod:`io` which provides the built-in :func:`open` makes less system calls
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when opening regular files as well as reading whole files. Reading a small
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operating system cached file in full is up to 15% faster.
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:func:`pathlib.Path.read_bytes` has the most optimizations for reading a
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file's bytes in full. (Contributed by Cody Maloney and Victor Stinner in
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:gh:`120754` and :gh:`90102`.)
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* Opening and reading files now executes fewer system calls.
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Reading a small operating system cached file in full is up to 15% faster.
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(Contributed by Cody Maloney and Victor Stinner
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in :gh:`120754` and :gh:`90102`.)
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pathlib
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-------
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* :func:`Path.read_bytes <pathlib.Path.read_bytes>` now uses unbuffered mode
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to open files, which is between 9% and 17% faster to read in full.
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(Contributed by Cody Maloney in :gh:`120754`.)
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pdb
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---
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* :mod:`pdb` now supports two backends, based on either
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:func:`sys.settrace` or :mod:`sys.monitoring`.
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Using the :ref:`pdb CLI <pdb-cli>` or :func:`breakpoint`
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will always use the :mod:`sys.monitoring` backend.
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Explicitly instantiating :class:`pdb.Pdb` and its derived classes
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will use the :func:`sys.settrace` backend by default, which is configurable.
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(Contributed by Tian Gao in :gh:`124533`.)
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uuid
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----
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* Improve generation of :class:`~uuid.UUID` objects via their dedicated
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functions:
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* :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are both roughly 40% faster
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for 16-byte names and 20% faster for 1024-byte names. Performance for
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longer names remains unchanged.
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* :func:`~uuid.uuid4` is 30% faster.
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* :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are now both roughly 40% faster
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for 16-byte names and 20% faster for 1024-byte names.
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Performance for longer names remains unchanged.
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(Contributed by Bénédikt Tran in :gh:`128150`.)
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* :func:`~uuid.uuid4` is now c. 30% faster.
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(Contributed by Bénédikt Tran in :gh:`128150`.)
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zlib
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----
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* On Windows, ``zlib-ng`` is now used as the implementation of the
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:mod:`zlib` module. This should produce compatible and comparable
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results with better performance, though it is worth noting that
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``zlib.Z_BEST_SPEED`` (1) may result in significantly less
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compression than the previous implementation (while also significantly
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reducing the time taken to compress).
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* On Windows, `zlib-ng <https://github.com/zlib-ng/zlib-ng>`__
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is now used as the implementation of the :mod:`zlib` module
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in the default binaries.
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There are no known incompatabilities between ``zlib-ng``
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and the previously-used ``zlib`` implementation.
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This should result in better performance at all compression levels.
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It is worth noting that ``zlib.Z_BEST_SPEED`` (``1``) may result in
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significantly less compression than the previous implementation,
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whilst also significantly reducing the time taken to compress.
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(Contributed by Steve Dower in :gh:`91349`.)
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