python / python/cpython

Attribute cache silently disabled after 1000 class edit, leading to poor performance

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interpreter-core performance type-bug
主要语言
Python
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描述

Bug report

Bug description:

After the changes from https://github.com/python/cpython/pull/114900 modifying a class more than 1000 times causes the attribute cache to be permanently disabled for that class. This was done to solve a crash when a class is modified more than 2**32 times ( https://github.com/python/cpython/issues/113462 )

It seems this number (1000) is too low for some real case applications.

I initially observed this as a ~50% performance regression in ERP5 performance tests when updating from python3.11 to python3.13. ERP5 is an application where classes are generated dynamically based on some configuration and some classes are modified more than 1000 times in the "normal" generation process.

This seems to also affect odoo, another ERP application, for this they resorted to using ctypes to reset the class version attribute ( https://github.com/odoo/odoo/pull/275640 )

My suggestion would be to use a much higher number before disabling the cache, 1000 is low.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

贡献指南

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从这里开始

  1. 先读完整个 Issue,再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库,在一个分支上完成修改。
  4. 提交 Pull Request,并在描述里引用这个 Issue 编号。

调研方向

首先查看 CPython pull request 114900 和 issue 113462,然后追踪类被反复修改后属性缓存是如何被禁用的。将 issue 中描述的 ERP5 和 Odoo 案例作为性能场景。完成的标准是在解决 issue 113462 中的崩溃场景的同时,避免所报告的回归问题。

由索引模型根据 Issue 内容生成。

评估

技术栈
python
领域
performance
Issue 类型
缺陷
难度
4/5
预计耗时
3-5 天
活跃度
活跃
描述清晰度
基本清楚
新手友好度
45/100

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