Re: [PATCH v5 00/21] mm/zsmalloc: add zpdesc memory descriptor for zswap.zpool

[Alex Shi]

On 8/7/24 1:17 PM, Sergey Senozhatsky wrote:
> On (24/08/06 12:34), Yosry Ahmed wrote:
> [..]
>>> So the sole reason for this work is as a part of the mem_desc
>>> conversion.  I'd like to hear from others who are to be involved in
>>> that conversion, please - it this patchset something we should be
>>> merging?
>>>
>>
>> Matthew asked an important question here that needs to be answered by
>> zsmalloc experts:
>> https://lore.kernel.org/lkml/Zq0zucMFsOwATsAC@xxxxxxxxxxxxxxxxxxxx/
> 
> Iff "zsmalloc experts" include me: I was under impression that there was
> a zsmalloc conversion plan otherwise this zpdesc effort is a little
> confusing, and, frankly, it hasn't appeared to me that this is "my problem"
> now.
> 
>> Do you allocate a per-page struct zpdesc, and have each one pointing
>> to a zspage?
> 
> I'm not very knowledgeable when it comes to memdesc, excuse my
> ignorance, and please feel free to educate me.
> 
> So I guess if we have something
> 
> struct zspage {
> 	..
> 	struct zpdesc *first_desc;
> 	..
> }
> 
> and we "chain" zpdesc-s to form a zspage, and make each of them point to
> a corresponding struct page (memdesc -> *page), then it'll resemble current
> zsmalloc and should work for everyone? I also assume for zspdesc-s zsmalloc
> will need to maintain a dedicated kmem_cache?

Yes, it would be a better way moving to memdesc, and using kmem_cache for zpdesc-s
seems workable.

Thanks
Alex