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PEP 703: Minor edits (#3143)

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Sam Gross 2023-05-11 14:11:40 -04:00 committed by GitHub
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@ -389,9 +389,9 @@ object's header: the "local" reference count, the "shared" reference
count, and the identifier of the owning thread. The BRC paper packs count, and the identifier of the owning thread. The BRC paper packs
these three things into a single 64-bit field. This PEP proposes using these three things into a single 64-bit field. This PEP proposes using
three separate fields in each object's header to avoid potential issues three separate fields in each object's header to avoid potential issues
due to reference count overflow. Additionally, the implementation due to reference count overflow. Additionally, the PEP supports a
proposed PEP supports a faster deallocation path that avoids an atomic faster deallocation path that avoids an atomic operation in the common
operation in the common case. case.
The proposed ``PyObject`` struct (also called ``struct _object``) is The proposed ``PyObject`` struct (also called ``struct _object``) is
below: below:
@ -941,7 +941,7 @@ from the memory allocator:
* ``list.contains`` * ``list.contains``
Borrowed References Borrowed References
------------------- '''''''''''''''''''
Per-object locking provides many of the important protections that the Per-object locking provides many of the important protections that the
GIL provides, but there are a few cases where it's not sufficient. GIL provides, but there are a few cases where it's not sufficient.
@ -975,7 +975,7 @@ dictionaries are effectively private (not accessible by other
threads). threads).
Python Critical Sections Python Critical Sections
------------------------ ''''''''''''''''''''''''
Straightforward per-object locking could introduce deadlocks that were Straightforward per-object locking could introduce deadlocks that were
not present when running with the GIL. Threads may hold locks for not present when running with the GIL. Threads may hold locks for
@ -1049,7 +1049,7 @@ two calls to ``Py_BEGIN_CRITICAL_SECTION`` because the inner critical
section may release the locks from the outer critical section. section may release the locks from the outer critical section.
Optimistically Avoiding Locking Optimistically Avoiding Locking
------------------------------- '''''''''''''''''''''''''''''''
A few operations on ``dict`` and ``list`` optimistically avoid A few operations on ``dict`` and ``list`` optimistically avoid
acquiring the per-object locks. They have a fast path operation that acquiring the per-object locks. They have a fast path operation that
@ -1163,7 +1163,7 @@ memory occupied by the Python object previously held a different
Mimalloc Changes for Optimistic ``list`` and ``dict`` Access Mimalloc Changes for Optimistic ``list`` and ``dict`` Access
------------------------------------------------------------ ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
The implementation requires additional constraints to the memory The implementation requires additional constraints to the memory
allocator, including some changes to the mimalloc code. Some allocator, including some changes to the mimalloc code. Some
@ -1198,7 +1198,7 @@ managed dictionaries.
Mimalloc Page Reuse Mimalloc Page Reuse
-------------------- '''''''''''''''''''
It is beneficial to keep the restrictions on mimalloc page reuse to a It is beneficial to keep the restrictions on mimalloc page reuse to a
short period of time to avoid increasing overall memory usage. short period of time to avoid increasing overall memory usage.
@ -1245,7 +1245,7 @@ empty blocks in the freed page, so the page can be used for any other
purpose or even returned to the operating system. purpose or even returned to the operating system.
Optimistic ``dict`` and ``list`` Access Summary Optimistic ``dict`` and ``list`` Access Summary
----------------------------------------------- '''''''''''''''''''''''''''''''''''''''''''''''
This PEP proposes a technique for thread-safe list and dictionary This PEP proposes a technique for thread-safe list and dictionary
accesses that typically avoids acquiring locks. This reduces accesses that typically avoids acquiring locks. This reduces
@ -1512,6 +1512,12 @@ Note that this PEP would not affect the performance of the default
.. _PR 19474: https://github.com/python/cpython/pull/19474 .. _PR 19474: https://github.com/python/cpython/pull/19474
Build Bots
==========
The stable build bots will also include ``--disable-gil`` builds.
How to Teach This How to Teach This
================= =================