Commit 58ba73e5 authored by Yosry Ahmed's avatar Yosry Ahmed Committed by Andrew Morton
Browse files

mm: z3fold: remove z3fold 

Patch series "mm: zswap: remove z3fold and zbud", v2.

After 2 cycles of deprecating z3fold, remove it as well as zbud (rationale
in specific patches).


This patch (of 2):

Z3fold has been marked as deprecated for 2 cycles and no one complained,
as expected.  As there are no known users, remove the code now.

Link: https://lkml.kernel.org/r/20250129180633.3501650-1-yosry.ahmed@linux.dev
Link: https://lkml.kernel.org/r/20250129180633.3501650-2-yosry.ahmed@linux.dev


Signed-off-by: default avatarYosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarNhat Pham <nphamcs@gmail.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: WANG Xuerui <kernel@xen0n.name>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 350dce38

CREDITS

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@@ -4311,6 +4311,7 @@ S: England 
N: Vitaly Wool

E: vitaly.wool@konsulko.com

D: Maintenance and development of zswap

D: Maintenance and development of z3fold



N: Chris Wright

E: chrisw@sous-sol.org

Documentation/mm/index.rst

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@@ -62,5 +62,4 @@ documentation, or deleted if it has served its purpose. 
   unevictable-lru

   vmalloced-kernel-stacks

   vmemmap_dedup

   z3fold

   zsmalloc

Documentation/mm/z3fold.rst

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======

z3fold

======



z3fold is a special purpose allocator for storing compressed pages.

It is designed to store up to three compressed pages per physical page.

It is a zbud derivative which allows for higher compression

ratio keeping the simplicity and determinism of its predecessor.



The main differences between z3fold and zbud are:



* unlike zbud, z3fold allows for up to PAGE_SIZE allocations

* z3fold can hold up to 3 compressed pages in its page

* z3fold doesn't export any API itself and is thus intended to be used

  via the zpool API.



To keep the determinism and simplicity, z3fold, just like zbud, always

stores an integral number of compressed pages per page, but it can store

up to 3 pages unlike zbud which can store at most 2. Therefore the

compression ratio goes to around 2.7x while zbud's one is around 1.7x.



Unlike zbud (but like zsmalloc for that matter) z3fold_alloc() does not

return a dereferenceable pointer. Instead, it returns an unsigned long

handle which encodes actual location of the allocated object.



Keeping effective compression ratio close to zsmalloc's, z3fold doesn't

depend on MMU enabled and provides more predictable reclaim behavior

which makes it a better fit for small and response-critical systems.

Documentation/translations/zh_CN/mm/index.rst

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@@ -58,7 +58,6 @@ Linux内存管理文档 
   remap_file_pages

   split_page_table_lock

   vmalloced-kernel-stacks

   z3fold

   zsmalloc



TODOLIST:

Documentation/translations/zh_CN/mm/z3fold.rst

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:Original: Documentation/mm/z3fold.rst



:翻译:



 司延腾 Yanteng Si <siyanteng@loongson.cn>



:校译:





======

z3fold

======



z3fold是一个专门用于存储压缩页的分配器。它被设计为每个物理页最多可以存储三个压缩页。

它是zbud的衍生物，允许更高的压缩率，保持其前辈的简单性和确定性。



z3fold和zbud的主要区别是:



* 与zbud不同的是，z3fold允许最大的PAGE_SIZE分配。

* z3fold在其页面中最多可以容纳3个压缩页面

* z3fold本身没有输出任何API，因此打算通过zpool的API来使用



为了保持确定性和简单性，z3fold，就像zbud一样，总是在每页存储一个整数的压缩页，但是

它最多可以存储3页，不像zbud最多可以存储2页。因此压缩率达到2.7倍左右，而zbud的压缩

率是1.7倍左右。



不像zbud（但也像zsmalloc），z3fold_alloc()那样不返回一个可重复引用的指针。相反，它

返回一个无符号长句柄，它编码了被分配对象的实际位置。



保持有效的压缩率接近于zsmalloc，z3fold不依赖于MMU的启用，并提供更可预测的回收行

为，这使得它更适合于小型和反应迅速的系统。