linux-kernel - Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for compress/decompress batching.

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Message-ID: <oiglkbyqz4cmzkjaguwgjkdu6dq6rj6oclppnd5xkwa7ekebwa@a4pbo4md3gvq>
Date: Sun, 23 Feb 2025 10:57:31 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Barry Song <21cnbao@...il.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>, 
	Minchan Kim <minchan@...nel.org>, "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	"hannes@...xchg.org" <hannes@...xchg.org>, "nphamcs@...il.com" <nphamcs@...il.com>, 
	"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>, "usamaarif642@...il.com" <usamaarif642@...il.com>, 
	"ryan.roberts@....com" <ryan.roberts@....com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, 
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, "davem@...emloft.net" <davem@...emloft.net>, 
	"clabbe@...libre.com" <clabbe@...libre.com>, "ardb@...nel.org" <ardb@...nel.org>, 
	"ebiggers@...gle.com" <ebiggers@...gle.com>, "surenb@...gle.com" <surenb@...gle.com>, 
	"Accardi, Kristen C" <kristen.c.accardi@...el.com>, "Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, 
	"Gopal, Vinodh" <vinodh.gopal@...el.com>
Subject: Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for
 compress/decompress batching.

On (25/02/23 08:24), Herbert Xu wrote:
> On Sat, Feb 22, 2025 at 09:31:41PM +0900, Sergey Senozhatsky wrote:
> >
> > The idea behind zram's code is that incompressible pages are not unusual,
> > they are quite usual, in fact,  It's not necessarily that the data grew
> > in size after compression, the data is incompressible from zsmalloc PoV.
> > That is the algorithm wasn't able to compress a PAGE_SIZE buffer to an
> > object smaller than zsmalloc's huge-class-watermark (around 3600 bytes,
> > depending on zspage chain size).  That's why we look at the comp-len.
> > Anything else is an error, perhaps a pretty catastrophic error.
> 
> If you're rejecting everything above the watermark then you should
> simply pass the watermark as the output length to the algorithm so
> that it can stop doing useless work once it gets past that point.

Makes sense.