[systemd-devel] [PATCH 1/2] journal: add LZ4 as optional compressor

[Reindl Harald]

Am 08.07.2014 12:22, schrieb Jon Severinsson:
> Am 06.07.2014 21:47, schrieb Lennart Poettering:
>> BTW, have you checked whether reuseing the XZ context might make the XZ
>> more competitive?
> 
> On Sun Jul 6 15:01:11 PDT 2014 Reindl Harald wrote:
>> please try a simple test compress 50 MB with XZ and GZ, LZO, LZ4
>> or BZIP2 - XZ is *magnitudes* slower in any case
> 
> Actually it is not, or rather, it is only that if you want it to be that.
> I did a quick comparison using the systemd 214 tar (30 MiB):
> xz -0 was 28% slower than lz4c -hc, but the result was 19% smaller. 
> xz -0 was even 44% faster than gzip -9, and the result was still 5% smaller.
> 
>> XZ is the wrong compression for anything where user feedback in time matters
> 
> No, xz -6 is the wrong compression *setting* for that use-case, but at a lower 
> setting xz is quite suitable even for that.
> 
>> even with no care about memory usage which also is part of the game finally
> 
> xz -0 needs about 3 MiB for compression, hardly a prohibitive requirement

you simply missed the benchmarks
see topic "compress: add benchmark-style test" yesterday

With 0:
XZ: compressed & decompressed 2535300963 bytes in 33.01s (73.25MiB/s), ...
LZ4: compressed & decompressed 2535303543 bytes in 1.31s (1838.75MiB/s), ..

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