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

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Message-ID: <aV3uXguDCaVAbY53@gondor.apana.org.au>
Date: Wed, 7 Jan 2026 13:25:50 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	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 Tue, Jan 06, 2026 at 04:24:45PM +0000, Yosry Ahmed wrote:
>
> Just to clarify, IIUC the SG support would mean that zram or zswap can
> pass a non-contiguous SG-list to the crypto API, regardless of
> compressor support. I assume that the crypto layer will either pass the
> SG-list as-is to the compressor if it supports it, or copy it into
> scratch space to be contiguous if needed.
>
> So zswap, for example, will get an SG list from zsmalloc and pass it
> directly to the crypto API for decompression. Then the effort to add
> support to compressors can be done separately.
> 
> Did I get this right?

Correct, you can already do that today with the scomp layer providing
the fallback linearisation.

Adding native SG support to LZO simply means removing the memcpy that
scomp would otherwise have to do.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt