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

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Message-ID: <dc1124d8-80d7-4cc3-8111-99ad7ee09ba4@redhat.com>
Date: Mon, 15 Jul 2024 18:21:25 +0200
From: David Hildenbrand <david@...hat.com>
To: Alex Shi <seakeel@...il.com>, 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, 42.hyeyoo@...il.com,
 Yosry Ahmed <yosryahmed@...gle.com>, nphamcs@...il.com
Subject: Re: [PATCH v3 00/20] mm/zsmalloc: add zpdesc memory descriptor for
 zswap.zpool

On 15.07.24 03:33, Alex Shi wrote:
> 
> 
> On 7/8/24 2:33 PM, alexs@...nel.org wrote:
>> From: Alex Shi (Tencent) <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 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?

Planning on taking a peek soon (busy traveling), but I'm hoping that 
people more familiar with the code can provide feedback.

-- 
Cheers,

David / dhildenb