linux-kernel - RE: [RFC PATCH 2/3] crypto: add by_n attribute to acomp

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Message-ID: <000001db10f6$cb3ca4b0$61b5ee10$@linux.intel.com>
Date: Fri, 27 Sep 2024 09:03:27 -0700
From: <bala.seshasayee@...ux.intel.com>
To: "'Barry Song'" <21cnbao@...il.com>
Cc: <tom.zanussi@...ux.intel.com>,
	<minchan@...nel.org>,
	<senozhatsky@...omium.org>,
	<hannes@...xchg.org>,
	<yosryahmed@...gle.com>,
	<nphamcs@...il.com>,
	<chengming.zhou@...ux.dev>,
	<herbert@...dor.apana.org.au>,
	<davem@...emloft.net>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"Jiang, Dave" <dave.jiang@...el.com>,
	"Feghali, Wajdi K" <wajdi.k.feghali@...el.com>,
	"Guilford, James" <james.guilford@...el.com>,
	"Gopal, Vinodh" <vinodh.gopal@...el.com>,
	"Caldwell, Heath" <heath.caldwell@...el.com>,
	"Sridhar, Kanchana P" <Kanchana.P.Sridhar@...el.com>,
	<linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>,
	<ryan.roberts@....com>,
	<linux-crypto@...r.kernel.org>,
	<dmaengine@...r.kernel.org>
Subject: RE: [RFC PATCH 2/3] crypto: add by_n attribute to acomp_req



> -----Original Message-----
> From: Barry Song <21cnbao@...il.com>
> Sent: Sunday, September 15, 2024 11:16 PM
> To: Andre Glover <andre.glover@...ux.intel.com>
> Cc: tom.zanussi@...ux.intel.com; minchan@...nel.org;
> senozhatsky@...omium.org; hannes@...xchg.org; yosryahmed@...gle.com;
> nphamcs@...il.com; chengming.zhou@...ux.dev;
> herbert@...dor.apana.org.au; davem@...emloft.net; Yu, Fenghua
> <fenghua.yu@...el.com>; Jiang, Dave <dave.jiang@...el.com>; Feghali, Wajdi K
> <wajdi.k.feghali@...el.com>; Guilford, James <james.guilford@...el.com>; Gopal,
> Vinodh <vinodh.gopal@...el.com>; Seshasayee, Bala
> <bala.seshasayee@...el.com>; Caldwell, Heath <heath.caldwell@...el.com>;
> Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>; linux-
> kernel@...r.kernel.org; linux-mm@...ck.org; ryan.roberts@....com; linux-
> crypto@...r.kernel.org; dmaengine@...r.kernel.org
> Subject: Re: [RFC PATCH 2/3] crypto: add by_n attribute to acomp_req
> 
> On Thu, May 2, 2024 at 5:46 AM Andre Glover <andre.glover@...ux.intel.com>
> wrote:
> >
> > Add the 'by_n' attribute to the acomp_req. The 'by_n' attribute can be
> > used a directive by acomp crypto algorithms for splitting compress and
> > decompress operations into "n" separate jobs.
> 
> Hi Andre,
> 
> I am definitely in favor of the patchset idea. However, I'm not convinced that a
> separate by_n API is necessary. Couldn’t this functionality be handled
> automatically within your driver? For instance, if a large folio is detected, could it
> automatically apply the by_n concept?
> 
> Am I overlooking something that makes exposing the API necessary in this case?

Hi Barry,

The 'deflate-iaa-canned' compression algorithm is fully compatible with the deflate standard. Andre's patchset introduces 'canned-by_n' as a new compression algorithm, which is not a deflate stream since it has a different header (for the by_n chunks).
The same 'canned-by_n' algorithm along with the value of the acomp_req ‘by_n’ attribute would be used to compress and decompress a given input buffer.
Furthermore, with a tunable 'by_n' , the user can experiment with different values of by_n for different mTHP sizes to understand trade-offs in performance vs. compression ratio.

Thanks
Bala