linux-kernel - Re: [RFC PATCH 2/2] zsmalloc: chain-length configuration should consider other metrics

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Message-ID: <llj3jf5evsp7f2wl2hmm6mouqzwzolvdnu4yquhxbgsgaqvsda@ltct5tqpzmyo>
Date: Wed, 7 Jan 2026 17:12:19 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, 
	Andrew Morton <akpm@...ux-foundation.org>, Nhat Pham <nphamcs@...il.com>, Minchan Kim <minchan@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Brian Geffon <bgeffon@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/2] zsmalloc: chain-length configuration should
 consider other metrics

On Wed, Jan 07, 2026 at 02:43:42PM +0900, Sergey Senozhatsky wrote:
> On (26/01/07 05:39), Yosry Ahmed wrote:
> > > On Tue, Jan 06, 2026 at 04:24:45PM +0000, Yosry Ahmed wrote:
> [..]
> > > Adding native SG support to LZO simply means removing the memcpy that
> > > scomp would otherwise have to do.
> > 
> > Yeah the effort to add native support to compressors can be done
> > separately. For zswap, I think the most common compressors are
> > actually zstd and LZ4.
> 
> I think it's the same for chromeos: lz4 (primary) and zstd
> (secondary/recompression).  zstd looks very complicated,
> not sure if we really want to diverge its codebase from
> the upstream (meta github repo).

I think there's value in using SG lists even if we do not have support
for lz4 or zstd. We'll remove the memcpy() logic in zsmalloc and the
kmap handling memcpy() in zswap if we just pass SG lists from zsmalloc
to zswap/zram.