linux-kernel - Re: [PATCH 00/15] add zpdesc memory descriptor for zswap.zpool

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Message-ID: <15ee2753-a3f6-4b41-8afa-344ce9154161@gmail.com>
Date: Fri, 21 Jun 2024 14:43:59 +0800
From: Alex Shi <seakeel@...il.com>
To: alexs@...nel.org, Vitaly Wool <vitaly.wool@...sulko.com>,
 Miaohe Lin <linmiaohe@...wei.com>, Andrew Morton
 <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, minchan@...nel.org, willy@...radead.org,
 senozhatsky@...omium.org, david@...hat.com, 42.hyeyoo@...il.com
Subject: Re: [PATCH 00/15] add zpdesc memory descriptor for zswap.zpool



On 6/21/24 1:46 PM, alexs@...nel.org wrote:
> From: Alex Shi <alexs@...nel.org>
> 
> 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@casper.infradead.org/
> 
> Here is a implement on z3fold 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 z3fold_desc, since there are 3 zpool
> usages under zswap, zbud, z3fold, zsmalloc. It looks like we may extend the
> zpdesc to zbud and zsmalloc, combined their usage into one.
BTW, 
Thanks for David and Willy's suggestion!
Since all zpool candidates are single page users, then we could use zpdesc to
descript them all in future.

Thanks

> 
> For zpdesc(page), z3fold just uses the 5th member zppage_flag, which
> match with page.private. Potentially uses the first member flags for
> headless PG_locked, list_head lru and page.mapping|PAGE_MAPPING_MOVABLE
> for page migration.> 
> This patachset could save 26Kbyetes z3fold.o size, basely saving come
> from the page to folio conversion.
> 
> Thanks a lot!
> Alex
> 
> Alex Shi (15):
>   mm/z3fold: add zpdesc struct and helper and use them in
>     z3fold_page_isolate
>   mm/z3fold: use zpdesc in z3fold_page_migrate
>   mm/z3fold: use zpdesc in z3fold_page_putback
>   mm/z3fold: use zpdesc in get/put_z3fold_header funcs
>   mm/z3fold: use zpdesc in init_z3fold_page
>   mm/z3fold: use zpdesc in free_z3fold_page
>   mm/z3fold: convert page to zpdesc in __release_z3fold_page
>   mm/z3fold: use zpdesc free_pages_work
>   mm/z3fold: use zpdesc in z3fold_compact_page and do_compact_page
>   mm/z3fold: use zpdesc in __z3fold_alloc
>   mm/z3fold: use zpdesc in z3fold_alloc
>   mm/z3fold: use zpdesc in free_z3fold_page and z3fold_free
>   mm/z3fold: use zpdesc in z3fold_map/z3fold_unmap
>   mm/z3fold: introduce __zpdesc_set_movable
>   mm/z3fold: introduce __zpdesc_clear_movable
> 
>  mm/z3fold.c | 190 +++++++++++++++++++++++++++-------------------------
>  mm/zpdesc.h |  87 ++++++++++++++++++++++++
>  2 files changed, 184 insertions(+), 93 deletions(-)
>  create mode 100644 mm/zpdesc.h
>