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

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Message-ID: <aWSAF4s7SYjWP9mq@gondor.apana.org.au>
Date: Mon, 12 Jan 2026 13:01:11 +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 Fri, Jan 09, 2026 at 04:02:51PM +0000, Yosry Ahmed wrote:
> 
> Herbert, do you mind taking a look at this? It looks sane to me except
> for one question below.

Looks alright to me too.

> > +		size_t sizes[2];
> > +
> > +		/* this object spans two pages */
> > +		sizes[0] = PAGE_SIZE - off;
> > +		sizes[1] = mem_len - sizes[0];
> > +
> > +		sg_init_table(sg, 2);
> > +		sg_set_page(sg, zpdesc_page(zpdesc), sizes[0], off);
> > +
> > +		zpdesc = get_next_zpdesc(zpdesc);
> > +		sg = sg_next(sg);
> 
> Is this stateful? Will the SG list be returned pointing at the second
> page now?

It makes no difference because we just called sg_init_table(sg, 2),
so sg_next(sg) is equivalent to &sg[1].

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