内存回收 - 基础

内存回收旧版笔记

按顺序来：

物理内存分配，了解几种内存回收方式的触发条件和路径
学习几种内存回收方式的区别，node_reclaim、direct_reclaim、kswapd reclaim
学习内存回收机制，先看关键流程，再深入函数细节。
1. scan_control
2. workingset
3. active/inactive 之间的平衡、file/anon 之间的平衡
4. shrink_lruvec()
  1. shrink_active_list
  2. shrink_inactive_list
5. shrink_slab
6. reclaim throttling
MGLRU
深入更底层
1. writeback
2. swap_cache, swap in/out
zswap
swap tableF

做一些总结：folio 在各个 active/inactive lru 链表之间的流转 lru，folio 的生命周期。

从 buddy 到 inactive
从 inactive promoted 到 active
从 active demoted 到 inactive
从 inactive evicted
从 inactive rotate 到 inactive head

挖掘演进历史总结每个函数的作用。vmscan.c swap.c workingset.c

内存回收的触发条件、回收方式

内存回收的触发路径。
- get_page_from_freelist() 时的 node_reclaim()，见 page_alloc 快速路径。
- kswapd 线程的间接回收。
- 慢速路径的直接回收。

关注于 struct scan_control

LRU 演进历程

2014-02-04 [patch 00/10] mm: thrash detection-based file cache sizing v9
- 2012-05-02 Better active/inactive list balancing [LWN.net]
- https://aistudio.google.com/prompts/1-YbmIW_NyHmLzDG_OqFLZl9VVOv72oxK
2020-05-20 [PATCH 00/14] mm: balance LRU lists based on relative thrashing v2 - Johannes Weiner
- https://aistudio.google.com/app/prompts/1b663zgF2iTeI-yuVMM0zYnaikIwa4LW6
2020-06-16 [PATCH for v5.8 0/3] fix for “mm: balance LRU lists based on relative thrashing” patchset - js1304
2020-07-23 [PATCH v7 0/6] workingset protection/detection on the anonymous LRU list - js1304 对匿名页的 workingset 保护
- 2020-03-10 Working-set protection for anonymous pages [LWN.net]
- 原先，匿名页在 refault 时，会无条件地进入 active list head，
2022-09-18 [PATCH mm-unstable v15 00/14] Multi-Gen LRU Framework - Yu Zhao 引入 MGLRU
- 2021-04-02 The multi-generational LRU [LWN.net]
- 2021-05-24 Multi-generational LRU: the next generation [LWN.net]
- 2022-05-12 Merging the multi-generational LRU [LWN.net]
2023-05-18 Page aging with hardware counters [LWN.net]

其他比较小的改动

2009-06-08 [PATCH 0/3] make mapped executable pages the first class citizen (with test cases) - Wu Fengguang
- 2009-05-19 Being nicer to executable pages [LWN.net]
- 可执行文件页更不容易 deactivate
2019-11-07 [PATCH 0/3] mm: fix page aging across multiple cgroups
2021-01-17 Linus Torvalds feb889fb40fa mm: don't put pinned pages into the swap cache
- 不把 pinned pages 放进 swap cache