Re: [PATCH 0/2] Squashfs: add LZ4 compression

[Martin Vath]

Hi:

> squashfs+lz4 / aufs to speed up my laptop

Squashfs proves its usefulness especially in combination
with aufs or overlayfs; I suppose that this combination
will become more popular with the spreading of overlayfs
(e.g. to save disk space etc.)

For users with such a combination, it is especially important
to get a fast (re)compression of huge directories.

The speed of LZ4 for compression in such a setting is really incredible.
Just for orientation for myself, I made a list of times/sizes
on some machines I had access to:

https://github.com/vaeth/squashmount/blob/master/compress.txt

(I do not claim that this is a scientific benchmark - just a
straightforward average over several runs).
The results for the kernel source and libreoffice are really
unbelievable, but I repeated them several times (and,
as you can see, for the kernel sources on different machines).

> From the user perspective, it is mainly important that
the files compressed in this way can be read by the kernel -
the decompression speed is here secondary, so I made no comparison
for this case, although lz4 is known to be very fast also
for decompression.

I would really like to see lz4 support included in the
squashfs kernel driver. I cannot imagine any negative consequences,
especially since squashfs and lz4 are in the kernel, anyway.

Sincerely
Martin Väth