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mk01 · 4th Apr, 2014, 05:43 PM

don't have (and don't plan benchs as general ones are as always on google) but lz4 was highly demanded few years back by zfs community and running apt-get install on XBian reminds more to ext4 times again.

speaking general facts, compress ratio is not suffering much (although our target was more "bandwidth" related than space saving), resource allocation goes minimal (lz4 by default works with minimal buffers - it works only with 8K internal buffer!) and decompression speed is more comparable to flat reading than the usual decompression speeds.

(when I cloned LZO -> LZ4, rootfs occupancy changed from 1.5GB to 1.6GB, cloning time was ~3/4, Gotham loads 2s faster, apt-get update is 28s vs 34s. so no revolution but definitely evolution for free. and RPI is more responsive if fully loaded by disk operations).

most importantly the patches to btrfs are really non-invasive to btrfs itself, it is clean add-on, not rewrite.

and as I wanted to try to match the archaic LZ4 to actual - LZ4 is since 3.11 part of Linus's tree. so maybe the patch at the end will be really minimal. will look at it right now.

from total 18K patch, 17K is lz4_compress and lz4_decompress function. the rest 1K is just .h LZ4 defs and new BTRFS flag.

https://code.google.com/p/lz4/