linux-kernel - Re: [PATCHv3 00/19] zram: convert to custom compression API and allow algorithms tuning

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Date: Fri, 10 May 2024 17:28:50 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org
Subject: Re: [PATCHv3 00/19] zram: convert to custom compression API and
 allow algorithms tuning

On (24/05/10 16:12), Herbert Xu wrote:
> On Fri, May 10, 2024 at 05:08:27PM +0900, Sergey Senozhatsky wrote:
> >
> > For some algorithms params needs to be set before ctx is created.
> > For example zstd, crypto/zstd calls zstd_get_params(ZSTD_DEF_LEVEL, 0)
> > to estimate workspace size, which misses the opportunity to configure
> > it an way zram/zswap can benefit from, because those work with PAGE_SIZE
> > source buffer.  So for zram zstd_get_params(ZSTD_DEF_LEVEL, PAGE_SIZE)
> > is much better (it saves 1.2MB per ctx, which is per-CPU in zram).  Not
> > to mention that zstd_get_params(param->level, 0) is what we need at the
> > end.
> 
> For these algorithms where the overhead of allocating a default
> set of parameters and then changing them on a setparam call is
> too high, we could stipulate that the tfm can only be used after
> a setparam call (just as we require a setkey before cipher ops).

OK.  I guess for drivers' params support (dictionaries handling etc.)
we take take some code from this series.  You mentioned acomp, does this
mean setparam is for async compression only?