jffs zlib tuning

imm ian at imm.uklinux.net
Mon Jan 7 15:04:18 EST 2008

> On 7 Jan 2008, at 19:28, Benjamin M. Schwartz wrote:
>> Nonetheless, I decided to benchmark the compressors on
>> http://xs-dev.laptop.org/~cscott/olpc/streams/joyride/build1513/ 
>> devel_jffs2/xo-1-olpc-stream-joyride-build-1513-20080105_1602- 
>> devel_jffs2-tree.tar.bz2
>> Results:
>> Uncompressed             732M
>> LZO -1 (fast)            345M
>> LZO -9 (slow)            298M
>> Gzip (defaults)          269M
>> Bzip2 (as downloaded)    236M
>> Note that fast vs. slow refers to compression speed.   
>> Decompression is
>> the same speed in either case.
>> These tests were run on the whole tar-file.  As noted by Bernie, the
>> differences would likely be smaller on 4KB blocks.
> I had some notes, which I can't now find, for a real-time sample  
> logger we built...
> Anyway, we did some tests compressing small blocks, and I am sure  
> we saw much less of a difference than Benjamin saw on his big block.
> Also, I'm pretty sure bzip2 fared very badly in our test, the small  
> blocks didn't suit it at all (and it was slower, of course.)
> Of course, the statistics of our sample data was probably not  
> representative, so YMMV...

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