Re: [PATCH v3 00/20] mm/zsmalloc: add zpdesc memory descriptor for zswap.zpool

[Alex Shi]

On 7/8/24 2:33 PM, alexs@xxxxxxxxxx wrote:
> From: Alex Shi (Tencent) <alexs@xxxxxxxxxx>
> 
> According to Metthew's plan, the page descriptor will be replace by a 8
> bytes mem_desc on destination purpose.
> https://lore.kernel.org/lkml/YvV1KTyzZ+Jrtj9x@xxxxxxxxxxxxxxxxxxxx/
> 
> Here is a implement on zsmalloc to replace page descriptor by 'zpdesc',
> which is still overlay on struct page now. but it's a step move forward
> above destination.
> 
> To name the struct zpdesc instead of zsdesc, since there are still 3
> zpools under zswap: zbud, z3fold, zsmalloc for now(z3fold maybe removed
> soon), and we could easyly extend it to other zswap.zpool in needs.
> 
> For all zswap.zpools, they are all using single page since often used
> under memory pressure. So the conversion via folio series helper is
> better than page's for compound_head check saving.
> 
> For now, all zpools are using some page struct members, like page.flags
> for PG_private/PG_locked. and list_head lru, page.mapping for page migration.
> 
> This patachset does not increase the descriptor size nor introduce any
> functional changes, and could save about 122Kbytes zsmalloc.o size.
> 
> Thanks
> Alex
> 

Any comments for this patchset?

Thanks
Alex

> ---
> v3->v2:
> - Fix LKP reported build issue
> - Update the Usage of struct zpdesc fields.
> - Rebase onto latest mm-unstable commit 2073cda629a4
> 
> v1->v2: 
> - Take Yosry and Yoo's suggestion to add more members in zpdesc,
> - Rebase on latest mm-unstable commit 31334cf98dbd
> ---
> 
> Alex Shi (Tencent) (9):
>   mm/zsmalloc: add zpdesc memory descriptor for zswap.zpool
>   mm/zsmalloc: use zpdesc in trylock_zspage/lock_zspage
>   mm/zsmalloc: convert create_page_chain() and its users to use zpdesc
>   mm/zsmalloc: rename reset_page to reset_zpdesc and use zpdesc in it
>   mm/zsmalloc: convert SetZsPageMovable and remove unused funcs
>   mm/zsmalloc: convert get/set_first_obj_offset() to take zpdesc
>   mm/zsmalloc: introduce __zpdesc_clear_movable
>   mm/zsmalloc: introduce __zpdesc_clear_zsmalloc
>   mm/zsmalloc: introduce __zpdesc_set_zsmalloc()
> 
> Hyeonggon Yoo (11):
>   mm/zsmalloc: convert __zs_map_object/__zs_unmap_object to use zpdesc
>   mm/zsmalloc: add and use pfn/zpdesc seeking funcs
>   mm/zsmalloc: convert obj_malloc() to use zpdesc
>   mm/zsmalloc: convert obj_allocated() and related helpers to use zpdesc
>   mm/zsmalloc: convert init_zspage() to use zpdesc
>   mm/zsmalloc: convert obj_to_page() and zs_free() to use zpdesc
>   mm/zsmalloc: add zpdesc_is_isolated/zpdesc_zone helper for
>     zs_page_migrate
>   mm/zsmalloc: convert __free_zspage() to use zdsesc
>   mm/zsmalloc: convert location_to_obj() to take zpdesc
>   mm/zsmalloc: convert migrate_zspage() to use zpdesc
>   mm/zsmalloc: convert get_zspage() to take zpdesc
> 
>  mm/zpdesc.h   | 146 ++++++++++++++++
>  mm/zsmalloc.c | 460 +++++++++++++++++++++++++++-----------------------
>  2 files changed, 398 insertions(+), 208 deletions(-)
>  create mode 100644 mm/zpdesc.h
>