linux-kernel - Re: [PATCH] mm/zswap: reduce the size of the compression buffer to a single page

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Message-ID: <CAKEwX=NLvQyZTqv15kACZP2wErO9hyv9W+0j-BWrgOh5ZX1LJA@mail.gmail.com>
Date: Wed, 20 Aug 2025 15:56:41 -0700
From: Nhat Pham <nphamcs@...il.com>
To: SeongJae Park <sj@...nel.org>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, yosry.ahmed@...ux.dev, 
	chengming.zhou@...ux.dev, herbert@...dor.apana.org.au, linux-mm@...ck.org, 
	kernel-team@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/zswap: reduce the size of the compression buffer to a
 single page

On Wed, Aug 20, 2025 at 3:47 PM SeongJae Park <sj@...nel.org> wrote:
>
> On Wed, 20 Aug 2025 11:15:47 -0700 Nhat Pham <nphamcs@...il.com> wrote:
>
> > Reduce the compression buffer size from 2 * PAGE_SIZE to only one page,
> > as the compression output (in the success case) should not exceed the
> > length of the input.
> >
> > In the past, Chengming tried to reduce the compression buffer size, but

Yeah, this should include the reference below. My bad. So it should be:

In the past, Chengming tried to reduce the compression buffer size
(see [1]), but

Andrew, would it be OK if you fix it for me when you put this patch in
your tree :) Or I can also send a new version if that's better. Thank
you!

> > ran into issues with the LZO algorithm (see [2]). Herbert Xu reported
> > that the issue has been fixed (see [3]). Now we should have the
> > guarantee that compressors' output should not exceed one page in the
> > success case, and the algorithm will just report failure otherwise.
> >
> > With this patch, we save one page per cpu (per compression algorithm).
> >
> > [1]: https://lore.kernel.org/linux-mm/20231213-zswap-dstmem-v4-1-f228b059dd89@bytedance.com/
>
> This is not mentioned anywhere.  Probably you added this as a reference for the
> past work from Chengming?

Thanks for taking a look, SJ!

>
> > [2]: https://lore.kernel.org/lkml/0000000000000b05cd060d6b5511@google.com/
> > [3]: https://lore.kernel.org/linux-mm/aKUmyl5gUFCdXGn-@gondor.apana.org.au/
> >
> > Co-developed-by: Chengming Zhou <chengming.zhou@...ux.dev>
> > Signed-off-by: Chengming Zhou <chengming.zhou@...ux.dev>
> > Signed-off-by: Nhat Pham <nphamcs@...il.com>
>
> Acked-by: SeongJae Park <sj@...nel.org>