linux-kernel - Re: Kernel compression benchmarks

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Date:   Wed, 01 Jul 2020 13:32:52 -0400
From:   "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To:     Gao Xiang <hsiangkao@....com>
Cc:     Chris Mason <clm@...com>, gregkh@...uxfoundation.org,
        Kees Cook <keescook@...omium.org>,
        Kernel Team <Kernel-team@...com>,
        Adam Borowski <kilobyte@...band.pl>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...nel.org, Nick Terrell <nickrterrell@...il.com>,
        Norbert Lange <nolange79@...il.com>,
        Petr Malat <oss@...at.biz>,
        Patrick Williams <patrick@...cx.xyz>,
        Patrick Williams <patrickw3@...com>, rmikey@...com,
        Sedat Dilek <sedat.dilek@...il.com>,
        Nick Terrell <terrelln@...com>, x86@...nel.org
Subject: Re: Kernel compression benchmarks

Excerpts from Gao Xiang's message of July 1, 2020 11:50 am:
>  Anyway, I think LZMA (xz) is still useful and which is more
>  friendly to fixed-sized output compression than Zstd yet (But
>  yeah, I'm not familar with all ZSTD internals. I will dig
>  into that if I've more extra time).

Yes, I agree. If you look at the graphs, LZMA2 (xz/7zip) still produces 
smaller results, even compared to zstd maximum settings, so definitely 
LZMA2 should be kept, at least for now. I am only suggesting removing 
LZMA, since it has no benefits over xz and zstd combination (bigger than 
xz, slower than zstd).

>> - modern compressors (xz, lz4, zstd) decompress about as fast for each 
>>   compression level, only requiring more memory
> 
>  lz4 has fixed sliding window (dictionary, 64k), so it won't
>  require more memory among different compression level when
>  decompressing.

Yes, this is true. I tried to simplify among all compressors, but I 
think I simplified too much. Thanks for clarifying.

Cheers,
Alex.