linux-kernel - Re: [PATCH v12 23/23] mm: zswap: Batched zswap_compress() with compress batching of large folios.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aPhpCGz1dWoZsMeH@gondor.apana.org.au>
Date: Wed, 22 Oct 2025 13:18:00 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, hannes@...xchg.org,
	yosry.ahmed@...ux.dev, nphamcs@...il.com, chengming.zhou@...ux.dev,
	usamaarif642@...il.com, ryan.roberts@....com, 21cnbao@...il.com,
	ying.huang@...ux.alibaba.com, akpm@...ux-foundation.org,
	senozhatsky@...omium.org, sj@...nel.org, kasong@...cent.com,
	linux-crypto@...r.kernel.org, davem@...emloft.net,
	clabbe@...libre.com, ardb@...nel.org, ebiggers@...gle.com,
	surenb@...gle.com, kristen.c.accardi@...el.com,
	vinicius.gomes@...el.com, wajdi.k.feghali@...el.com,
	vinodh.gopal@...el.com
Subject: Re: [PATCH v12 23/23] mm: zswap: Batched zswap_compress() with
 compress batching of large folios.

On Thu, Sep 25, 2025 at 08:35:02PM -0700, Kanchana P Sridhar wrote:
>
> Another initialization level optimization that happens in
> zswap_cpu_comp_prepare() is, only for batching compressors, we allocate
> extra memory for "batch-size" int pointers in the
> @acomp_ctx->req->__ctx[] that are statically set to track the output SG
> lists' lengths. This optimization was necessary to avoid the latency

There is no need for this allocation.  Just store the output lengths
in each destination scatterlist entry.

Before the call to acomp, the destination SG list should contain as
many elements as the number of units.  On return, the dst lengths
should be stored in each destination SG entry.

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