linux-kernel - Re: [PATCHv2 00/17] zram: convert to custom comp API and allow algorithms configuration

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Message-ID: <20240508074128.GG8623@google.com>
Date: Wed, 8 May 2024 16:41:28 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCHv2 00/17] zram: convert to custom comp API and allow
 algorithms configuration

On (24/05/06 16:58), Sergey Senozhatsky wrote:
> 	This patch set moves zram from crypto API to a custom compression
> API which allows us to tune and configure compression algorithms,
> something that crypto API, unfortunately, doesn't support. Basically,
> this seroes brings back the bits of comp "backend" code that we had
> many years ago. This means that if we want zram to support new
> compression algorithms we need to implement corresponding backends.
> 
>         Currently, zram supports a pretty decent number of comp backends:
> lzo, lzorle, lz4, lz4hc, 842, deflate, zstd
> 
>         At this point we handle 2 parameters: a compression level and
> a pre-trained compression dictionary. Which seems like a good enough
> start. The list will be extended in the future.
> 
> Examples:
> 
> - changes default compression level
>         echo "algo=zstd level=11" > /sys/block/zram0/comp_algorithm
> 
> - passes path to a pre-trained dictionary
>         echo "algo=zstd dict=/etc/dictionary" > /sys/block/zram0/comp_algorithm

I'll send v3 shortly, which adds pre-trained dictionary support to
lz4 and lz4hc compression backends. Apparently lz4/lz4hc can use
dictionaries pre-trained with zstd --init, just like zstd.