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description: scheduler and memory

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Cheng Jian
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study/kernel/00-DESCRIPTION/DEBUGGING.md
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@@ -198,6 +198,15 @@ Facebook 在 2018 年开源了一套解决重要计算集群管理问题的 Linu
| 2019/02/12 | Rasmus Villemoes <linux@rasmusvillemoes.dk> | [various dynamic_debug patches](https://lore.kernel.org/patchwork/patch/1041363) | NA | v1 ☑ 5.1-rc1 | [Patchwork v4,00/14](https://lore.kernel.org/patchwork/patch/1041363) |
| 2019/04/09 | Rasmus Villemoes <linux@rasmusvillemoes.dk> | [implement DYNAMIC_DEBUG_RELATIVE_POINTERS](https://lore.kernel.org/patchwork/patch/1059829) | 实现 DYNAMIC_DEBUG_RELATIVE_POINTERS | v1 ☐ | [Patchwork ](https://lore.kernel.org/patchwork/patch/1059829) |
# 8 DRGN
-------
[LWN/A kernel debugger in Python: drgn(https://lwn.net/Articles/789641)
[LWN: 想用python命令来调试kernel吗？drgn就是了！](https://blog.csdn.net/Linux_Everything/article/details/93270705)
# 7 OTHER
-------
study/kernel/00-DESCRIPTION/LOCKING.md
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@@ -32,7 +32,7 @@ blogexcerpt: 虚拟化 & KVM 子系统
<br>
2 **虚拟化子系统**
2 **锁**
=====================
@@ -150,6 +150,13 @@ PV_SPINLOCKS 的合入引起了[性能问题 Performance overhead of paravirt_op
| 2021/05/14 | Alex Kogan <alex.kogan@oracle.com> | [Add NUMA-awareness to qspinlock](https://lore.kernel.org/patchwork/cover/1428910) | NUMA 感知的 spinlock, 基于 CNA. | v15 ☐ | [PatchWork v15](https://lore.kernel.org/patchwork/cover/1428910) |
# 2 RWSEM
-------
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2020/11/21 | Waiman Long <longman@redhat.com> | [locking/rwsem: Rework reader optimistic spinning](https://lore.kernel.org/patchwork/cover/1342950) | 当读者的评论部分很短, 周围没有那么多读者时, 读者乐观旋转(osq_lock)是有帮助的. 它还提高了读者获得锁的机会, 因为写入器乐观旋转对写入器的好处远远大于读者. 由于提交d3681e269fff ("locking/rwsem: Wake up almost all reader in wait queue"), 所有等待的reader都会被唤醒, 这样它们就都能获得读锁并并行运行. 当竞争的读者数量很大时, 允许读者乐观自旋很可能会导致读者碎片, 多个较小的读者组可以以顺序的方式(由写入器分隔)获得读锁. 这降低了读者的并行性. 解决这个缺点的一种可能方法是限制能够进行乐观旋转的读者的数量(最好是一个). 这些读者作为等待队列中所有等待的读者的代表, 因为一旦获得锁, 它们将唤醒所有等待的读者. | v2 ☐ | [PatchWork v2,0/5](https://lore.kernel.org/patchwork/cover/1342950) |
<br>
* 本作品/博文 ( [AderStep-紫夜阑珊-青伶巷草 Copyright ©2013-2017](http://blog.csdn.net/gatieme) ), 由 [成坚(gatieme)](http://blog.csdn.net/gatieme) 创作.
study/kernel/00-DESCRIPTION/MEMORY_MANAGER.md
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@@ -110,16 +110,25 @@ Mainline Merge Window - Merge branch 'akpm' (patches from Andrew)
## 0.4 社区的内存管理领域的开发者
-------
- [x] [David Rientjes <rientjes@google.com>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=6580&state=*&archive=both&param=4&page=1)
| developer | git |
|:---------:|:---:|
| [David Rientjes <rientjes@google.com>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=6580&state=*&archive=both&param=4&page=1) | NA |
| [Mel Gorman <mgorman@techsingularity.net>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=19167&state=*&archive=both&param=3&page=1) | [git.kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git) |
| [Minchan Kim <minchan@kernel.org>](https://lore.kernel.org/patchwork/project/lkml/list/?series=&submitter=13305&state=*&q=&archive=both&delegate=) | NA |
| [Joonsoo Kim](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=13703&state=%2A&archive=both) | NA |
| [Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=4430&state=%2A&archive=both) | NA |
- [x] [Mel Gorman <mgorman@techsingularity.net>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=19167&state=*&archive=both&param=3&page=1)
- [x] [Minchan Kim <minchan@kernel.org>](https://lore.kernel.org/patchwork/project/lkml/list/?series=&submitter=13305&state=*&q=&archive=both&delegate=)
## 0.5 社区地址
-------
- [x] [Joonsoo Kim](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=13703&state=%2A&archive=both)
- [x] [Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>](https://lore.kernel.org/patchwork/project/lkml/list/?submitter=4430&state=%2A&archive=both)
| 描述 | 地址 |
|:---:|:----:|
| WebSite | [linux-mm](https://www.linux-mm.org) |
| PatchWork | [PatchWork](https://patchwork.kernel.org/project/linux-mm/list/?archive=both&state=*) |
| 邮件列表 | linux-mm@kvack.org |
| maintainer branch | [Github](https://github.com/hnaz/linux-mm)
## 0.5 目录
-------
@@ -198,7 +207,9 @@ Linux 一开始是在一台i386上的机器开发的, i386 的硬件页表是2
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2021/04/14 | "Matthew Wilcox (Oracle)" <willy@infradead.org> | [Memory folios](https://lwn.net/Articles/849538) | NA | v11 ☐ | [PatchWork v11](https://lore.kernel.org/patchwork/cover/1446440), [LWN](https://lwn.net/Articles/849538) |
| 2021/06/22 | "Matthew Wilcox (Oracle)" <willy@infradead.org> | [Memory folios](https://lwn.net/Articles/849538) | NA | v13 ☐ | [PatchWork v13](https://lore.kernel.org/patchwork/cover/1450139), [LWN](https://lwn.net/Articles/849538) |
| 2021/06/22 | "Matthew Wilcox (Oracle)" <willy@infradead.org> | [Folio-enabling the page cache](https://lwn.net/Articles/1450196) | NA | v2 ☐ | [PatchWork v2](https://lore.kernel.org/patchwork/cover/1450196), [PatchWork v2](https://patchwork.kernel.org/project/linux-mm/cover/20210622121551.3398730-1-willy@infradead.org) |
| 2021/06/30 | "Matthew Wilcox (Oracle)" <willy@infradead.org> | [Folio conversion of memcg](https://lwn.net/Articles/1450196) | NA | v3 ☐ | [PatchWork v3](https://patchwork.kernel.org/project/linux-mm/cover/20210630040034.1155892-1-willy@infradead.org) |
@@ -336,7 +347,7 @@ a206231bbe6 [PATCH] hot-n-cold pages: page allocator core
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2017/10/17 | Jan Kara <jack@suse.cz> | [Speed up page cache truncation v2](https://patchwork.kernel.org/project/linux-fsdevel/patch/20171017162120.30990-2-jack@suse.cz) | NA | v2 ☑ 5.11-rc1 | [PatchwWork v2](https://patchwork.kernel.org/project/linux-fsdevel/patch/20171017162120.30990-2-jack@suse.cz) |
| 2017/10/18 | Mel Gorman <mgorman@techsingularity.net> | [Follow-up for speed up page cache truncation v2](https://lore.kernel.org/patchwork/cover/842268) | NA | v2 ☑ 4.15-rc1 | [PatchwWork v2](https://lore.kernel.org/patchwork/cover/842268) |
| 2016/12/01 | Vlastimil Babka <vbabka@suse.cz> | [disable pcplists during memory offline](https://lore.kernel.org/patchwork/cover/1336780) | 当内存下线的时候, 禁用 PCP | v3 ☑ 5.11-rc1 | [v4](https://lore.kernel.org/patchwork/cover/1336780) |
| 2020/11/11 | Vlastimil Babka <vbabka@suse.cz> | [disable pcplists during memory offline](https://lore.kernel.org/patchwork/cover/1336780) | 当内存下线的时候, 禁用 PCP | v3 ☑ [5.11-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [v4](https://lore.kernel.org/patchwork/cover/1336780) |
* [High-order per-cpu page allocator](https://lore.kernel.org/patchwork/patch/740275)
@@ -373,6 +384,19 @@ a206231bbe6 [PATCH] hot-n-cold pages: page allocator core
| 2020/03/20 | Mel Gorman | [mm/page_alloc: Add a bulk page allocator -fix -fix](https://lore.kernel.org/patchwork/cover/1405057) | Bulk memory allocation 的第二组修复补丁 | v1 ☐ | [RFC](https://lore.kernel.org/patchwork/cover/1405057) |
percpu 页分配器(PCP)旨在减少对区域锁的争用, 但是 batch 和 high 的大小已经过时了,既不考虑区域大小, 也不考虑一个区域的本地cpu数量. 随着更大的区域和每个节点更多的 cpu, 争用情况越来越糟. 而且, vm.percpu_pagelist_fraction 同时调整批处理和高值, 这意味着 sysctl 可以减少区域锁争用，但也会增加分配延迟.
Mel Gorman 开发的 [Calculate pcp->high based on zone sizes and active CPUs](https://lore.kernel.org/patchwork/cover/1435878) 将 pcp->high 从 pcp->batch 中分离出来, 然后根据 local zone 的大小扩展 pcp->high, 对活动cpu的回收和计算影响有限, 但 pcp->batch 保持静态. 它还根据最近的释放模式调整可以在 PCP 列表上的页面数量.
其动机部分是为了调整以适应更大的内存大小, 但也受到这样一个事实的驱动: 通过 `release_pages()` 批量释放页面常常显示区域争用是问题的主要部分. 另一个是基于旧内核的bug报告，在旧内核中，一个多tb的进程可能需要几分钟才能退出. 一种变通方法是使用 vm.percpu_pagelist_fraction 来增加 pcp->high, 但是测试表明, 由于分配延迟的增加, 生产工作负载不能使用相同的值. 不幸的是, 我不能自己重现这个测试用例, 因为多tb的机器正在积极使用中, 但它应该可以缓解问题.
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2021/05/25 | Mel Gorman <mgorman@techsingularity.net> | [Making high and batch sizes of per_cpu_pagelists configurable](https://lore.kernel.org/patchwork/cover/47659) | 引入了 percpu_pagelist_fraction 来调整各个 zone PCP 的 high, 同时将 batch 值设置为 min(high/4, ) | v1 ☑ 5.14-rc1 | [RFC](https://lore.kernel.org/patchwork/cover/47659) |
| 2021/05/25 | Mel Gorman <mgorman@techsingularity.net> | [Calculate pcp->high based on zone sizes and active CPUs](https://lore.kernel.org/patchwork/cover/1435878) | pcp->high 和 pcp->batch 根据 zone 内内存的大小进行调整. 移除了不适用的 vm.percpu_pagelist_fraction 参数. | v2 ☑ 5.14-rc1 | [PatchWork v2](https://lore.kernel.org/patchwork/cover/1435878) |
| 2021/06/03 | Mel Gorman <mgorman@techsingularity.net> | [Allow high order pages to be stored on PCP v2](https://lore.kernel.org/patchwork/cover/1440776) | PCP 支持缓存高 order 的页面. | v2 ☑ 5.14-rc1 | [PatchWork v2](https://lore.kernel.org/patchwork/cover/1440776) |
### 2.1.5 ALLOC_NOFRAGMENT 优化
-------
@@ -629,7 +653,7 @@ https://lore.kernel.org/patchwork/cover/668967
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2019/04/06 | "Uladzislau Rezki (Sony)" <urezki@gmail.com> | [improve vmap allocation](https://lore.kernel.org/patchwork/cover/1059021) | 实现 SLOB 分配器 | v2 ☑ [5.2-rc7](https://kernelnewbies.org/Linux_5.2#Memory_management) | [PatchWork RFC](https://lore.kernel.org/patchwork/cover/1002038)<br>*-*-*-*-*-*-*-* <br>[PatchWork RFC v4](https://lore.kernel.org/patchwork/cover/1028793), [PatchWork v2](https://lore.kernel.org/patchwork/cover/1059021) |
| 2019/01/03 | "Uladzislau Rezki (Sony)" <urezki@gmail.com> | [test driver to analyse vmalloc allocator](https://lore.kernel.org/patchwork/cover/1059021) | 实现一个 test 驱动来帮助分析和测试 vmalloc | RFC v4 ☐ | [PatchWork RFC v4](https://lore.kernel.org/patchwork/cover/1028793) |
| 2021/03/17 | Nicholas Piggin <npiggin@gmail.com> | [huge vmalloc mappings](https://lore.kernel.org/patchwork/cover/1397495) | vmalloc 支持透明大页 | v13 ☑ 5.13-rc1 | [PatchWork v13](https://lore.kernel.org/patchwork/cover/1397495) |
| 2021/03/17 | Nicholas Piggin <npiggin@gmail.com> | [huge vmalloc mappings](https://lore.kernel.org/patchwork/cover/1397495) | vmalloc 支持透明大页 | v13 ☑ [5.13-rc1](https://kernelnewbies.org/Linux_5.13#Memory_management) | [PatchWork v13,00/14](https://patchwork.kernel.org/project/linux-mm/cover/20210317062402.533919-1-npiggin@gmail.com/) |
| 2021/03/24 | "Matthew Wilcox (Oracle)" <willy@infradead.org> | [vmalloc: Improve vmalloc(4MB) performance](https://lore.kernel.org/patchwork/cover/1401688) | 加速 4MB vmalloc 分配. | v2 ☑ 5.13-rc1 | [PatchWork v2](https://lore.kernel.org/patchwork/cover/1401688) |
@@ -1289,8 +1313,12 @@ Linux 内核在脏页数量到达一定门槛时, 或者用户在命令行输入
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2018/06/11 | Matthew Wilcox <willy@infradead.org> | [Convert page cache to XArray](https://lore.kernel.org/patchwork/cover/951137) | 将 page cahce 的组织结构从 radix tree 切换到 [xarray](https://lwn.net/Articles/745073). | v13 ☑ 2.5.8 | [PatchWork](https://lore.kernel.org/patchwork/cover/951137) |
| 2020/06/10 | Matthew Wilcox <willy@infradead.org> | [Large pages in the page cache](https://lore.kernel.org/patchwork/cover/1254710) | NA | v6 ☐ | [PatchWork RFC,v6,00/51](https://patchwork.kernel.org/project/linux-mm/cover/20200610201345.13273-1-willy@infradead.org) |
| 2020/06/29 | Matthew Wilcox <willy@infradead.org> | [THP prep patches](https://patchwork.kernel.org/project/linux-mm/cover/20200629151959.15779-1-willy@infradead.org/) | NA | v1 ☑ 2.5.8 | [PatchWork](https://patchwork.kernel.org/project/linux-mm/cover/20200629151959.15779-1-willy@infradead.org) |
https://lore.kernel.org/patchwork/cover/1324435/
## 6.2 页面预读(readahead)
-------
@@ -1596,6 +1624,22 @@ RMAP 反向映射是一种物理地址反向映射虚拟地址的方法.
| 2014/05/23 | Davidlohr Bueso <davidlohr@hp.com> | [mm: i_mmap_mutex to rwsem](https://lore.kernel.org/patchwork/cover/466974) | 2012 年 Ingo 将 anon-vma lock 从 mutex 转换到了 rwsem 锁. i_mmap_mutex 与 anon-vma 有类似的职责, 保护文件支持的页面. 因此, 我们可以使用类似的锁定技术 : 将互斥锁转换为rwsem, 并在可能的情况下共享锁. | RFC ☐ | [PatchWork](https://lore.kernel.org/patchwork/cover/466974) |
## 8.4 Mremapping
-------
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2020/10/14 | Kalesh Singh <kaleshsingh@google.com> | [Speed up mremap on large regions](https://lore.kernel.org/patchwork/cover/1321018) | mremap PUD 映射优化, 可以加速映射大块地址时的速度. 如果源地址和目的地址是 PMD/PUD 对齐和 PMD/PUD 大小, mremap 的耗时时间可以通过移动 PMD/PUD 级别的表项来优化. 允许在 arm64 和 x86 上的 PMD 和 PUD 级别移动. 其他支持这种类型移动且已知安全的体系结构也可以通过启用 HAVE_MOVE_PMD 和 HAVE_MOVE_PUD 来选择这些优化。 | v4 ☑ | [PatchWork v4,0/5](https://patchwork.kernel.org/project/linux-mm/cover/20201014005320.2233162-1-kaleshsingh@google.com/) |
## 8.5 filemapping
-------
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2020/10/25 | Kalesh Singh <kaleshsingh@google.com> | [generic_file_buffered_read() improvements](https://lore.kernel.org/patchwork/cover/1324435) | filemap 的批量内存分配和拷贝. | v4 ☑ [5.11-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [PatchWork v2,0/2](https://lore.kernel.org/patchwork/cover/1324435) |
# 9 内存控制组 MEMCG (Memory Cgroup)支持
-------
@@ -1618,6 +1662,7 @@ RMAP 反向映射是一种物理地址反向映射虚拟地址的方法.
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2007/01/15 | Roy Huang <royhuang9@gmail.com> | [Provide an interface to limit total page cache.](https://lore.kernel.org/patchwork/cover/72078) | 限制 page cache 的内存占用. | RFC ☐ | [PatchWork RFC](https://lore.kernel.org/patchwork/cover/72078) |
| 2007/01/24 | Christoph Lameter <clameter@sgi.com> | [Limit the size of the pagecache](https://lore.kernel.org/patchwork/cover/72581) | 限制 page cache 的内存占用. | RFC ☐ | [PatchWork RFC](https://lore.kernel.org/patchwork/cover/72581) |
| 2014/06/16 | Xishi Qiu <qiuxishi@huawei.com> | [Limit the size of the pagecache](https://lore.kernel.org/patchwork/cover/72581) | 限制 page cache 的内存占用. | RFC ☐ | [PatchWork RFC](https://lore.kernel.org/patchwork/cover/72581) |
| 2014/06/16 | Xishi Qiu <qiuxishi@huawei.com> | [mm: add page cache limit and reclaim feature](https://lore.kernel.org/patchwork/cover/473535) | 限制 page cache 的内存占用. | v1 ☐ | [PatchWork](https://lore.kernel.org/patchwork/cover/416962)<br>*-*-*-*-*-*-*-* <br>[openEuler 4.19](https://gitee.com/openeuler/kernel/commit/6174ecb523613c8ed8dcdc889d46f4c02f65b9e4) |
| 2019/02/23 | Chunguang Xu <brookxu@tencent.com> | [pagecachelimit: limit the pagecache ratio of totalram](http://github.com/tencent/TencentOS-kernel/commit/6711b34671bc658c3a395d99aafedd04a4ebbd41) | 限制 page cache 的内存占用. | NA | [pagecachelimit: limit the pagecache ratio of totalram](http://github.com/tencent/TencentOS-kernel/commit/6711b34671bc658c3a395d99aafedd04a4ebbd41) |
@@ -1672,7 +1717,7 @@ git://github.com/glommer/linux.git kmemcg-slab
| 2020/06/23 | Glauber Costa <glommer@parallels.com> | [kmem controller for memcg](https://lwn.net/Articles/516529) | memcg 支持对内核内存(kmem)进行统计, memcg 开始支持统计两种类型的内核内存使用 : 内核栈 和 slab. 这些限制对于防止 fork 炸弹(bombs)等事件很有用. | v6 ☑ 3.8-rc1 | [PatchWork v5 kmem(stack) controller for memcg](https://lore.kernel.org/patchwork/cover/333535), [PatchWork v5 slab accounting for memcg](https://lore.kernel.org/patchwork/cover/334479/)<br>*-*-*-*-*-*-*-* <br>[PatchWork v6](https://lore.kernel.org/patchwork/cover/337780) |
| 2020/06/23 | Roman Gushchin <guro@fb.com> | [The new cgroup slab memory controller](https://lore.kernel.org/patchwork/cover/1261793) | 将 SLAB 的统计跟踪统计从页面级别更改为到对象级别. 它允许在 memory cgroup 之间共享 SLAB 页. 这一变化消除了每个 memory cgroup 每个重复的每个 cpu 和每个节点 slab 缓存集, 并为所有内存控制组建立了一个共同的每个cpu和每个节点slab缓存集. 这将显著提高 SLAB 利用率(最高可达45%), 并相应降低总的内核内存占用. 测试发现不可移动页面数量的减少也对内存碎片产生积极的影响. | v7 ☑ 5.9-rc1 | [PatchWork v7](https://lore.kernel.org/patchwork/cover/1261793/) |
| 2015/11/10 | Roman Gushchin <guro@fb.com> | [memcg/kmem: switch to white list policy](https://lore.kernel.org/patchwork/cover/616606) | 所有的 kmem 分配(即每次 kmem_cache_alloc、kmalloc、alloc_kmem_pages调用)都会自动计入内存 cgroup. 如果出于某些原因, 呼叫者必须明确选择退出. 这样的设计决策会导致以下许多个问题, 因此该补丁切换为白名单策略. 现在 kmalloc 用户必须通过传递 __GFP_ACCOUNT 标志来显式标记. | v7 ☑ 5.9-rc1 | [PatchWork v7](https://lore.kernel.org/patchwork/cover/616606) |
| 2021/05/06 | Waiman Long <longman@redhat.com> | [mm/memcg: Reduce kmemcache memory accounting overhead](https://lore.kernel.org/patchwork/cover/1422112) | 降低 kmemcache 统计的消耗. | v6 ☐ | [PatchWork v6](https://lore.kernel.org/patchwork/cover/1422112) |
| 2021/05/06 | Waiman Long <longman@redhat.com> | [The new cgroup slab memory controller](https://lore.kernel.org/patchwork/cover/1422112) | [The new cgroup slab memory controller](https://lore.kernel.org/patchwork/cover/1261793) 合入后, 不再需要为每个 MEMCG 使用单独的 kmemcache, 从而减少了总体的内核内存使用. 但是, 我们还为每次调用 kmem_cache_alloc() 和 kmem_cache_free() 增加了额外的内存开销. 参见 [10befea91b: hackbench.throughput -62.4% regression](https://lore.kernel.org/lkml/20210114025151.GA22932@xsang-OptiPlex-9020) 和 [memcg: performance degradation since v5.9](https://lore.kernel.org/linux-mm/20210408193948.vfktg3azh2wrt56t@gabell/T/#u). 这组补丁通过降低了 kmemcache 统计的开销. 缓解了这个问题. | v7 ☑ 5.9-rc1 | [PatchWork v7](https://lore.kernel.org/patchwork/cover/1422112) |
## 9.4 memcg LRU list
@@ -2140,6 +2185,15 @@ SLAB 作为一个相对独立的子模块, 一直有自己完善的调试支持,
总的来说, 它利用了 GCC 5.0的新特性, 可对内核内存进行 Instrumentaion, 编译器可以在访问内存前插入指令, 从而检测该次访问是否合法. 对比前述的 KMEMCHECK 要用到 CPU 的陷阱指令处理和单步调试功能, KASan 是在编译时加入了探针, 因此它的性能更快.
ARM 引入了一个[内存标签扩展](https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/enhancing-memory-safety)的硬件特性. 然后 Google 的 [Andrey Konovalov](https://github.com/xairy/linux/)基于此硬件特性重写了 KASan. 实现了 [hardware tag-based mode 的 KASan](https://lore.kernel.org/patchwork/cover/1344197).
| 时间 | 作者 | 特性 | 描述 | 是否合入主线 | 链接 |
|:----:|:----:|:---:|:----:|:---------:|:----:|
| 2020/11/23 | Andrey Konovalov <andreyknvl@google.com> | [kasan: add hardware tag-based mode for arm64](https://lore.kernel.org/patchwork/cover/1344197) | NA | v11 ☑ [5.11-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [PatchWork mm,v11,00/42](https://patchwork.kernel.org/project/linux-mm/cover/cover.1606161801.git.andreyknvl@google.com) |
| 2020/11/23 | Andrey Konovalov <andreyknvl@google.com> | [kasan: boot parameters for hardware tag-based mode](https://lore.kernel.org/patchwork/cover/1344258) | NA | v4 ☑ [5.11-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [PatchWork mm,v4,00/19](https://patchwork.kernel.org/project/linux-mm/patch/748daf013e17d925b0fe00c1c3b5dce726dd2430.1606162397.git.andreyknvl@google.com/) |
| 2021/01/15 | Andrey Konovalov <andreyknvl@google.com> | [kasan: HW_TAGS tests support and fixes](https://lore.kernel.org/patchwork/cover/1366086) | NA | v4 ☑ [5.12-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [PatchWork mm,v4,00/15](https://patchwork.kernel.org/project/linux-mm/cover/cover.1610733117.git.andreyknvl@google.com) |
| 2021/02/05 | Andrey Konovalov <andreyknvl@google.com> | [kasan: optimizations and fixes for HW_TAGS](https://lore.kernel.org/patchwork/cover/1376340) | NA | v3 ☑ [5.12-rc1](https://kernelnewbies.org/Linux_5.11#Memory_management) | [PatchWork mm,v3,mm,00/13](https://patchwork.kernel.org/project/linux-mm/cover/cover.1612546384.git.andreyknvl@google.com) |
### 13.3.5 KFENCE 一个新的内存安全检测工具
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