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scripts/image: use 256kb blocksize for squashfs images #2992
Squashfs allows configuring a blocksize between 4KB and 1MB. The default is
Gzip decreases image by ~700KB.
Benchmarking device is an RPi3 running an AArch32 build of LE-9 git from 9/19/18. Test data is a LE9 git filesystem (the /etc and /usr directories - 303MB) from the end of August; the same used for compression level testing. Filename is squashfs-compression method-compression level-blocksize. UTIME is access time to decompress and dump the image to /dev/null.
Benchmarking scripts: https://github.com/antonlacon/squashfs-experiments/tree/LE-testing
One thought might be to make the blocksize configurable - 256KB may not be the sweetspot for all compression algos. Adding
I know it's the same blocksize for
In fact we probably only want to set
as this would allow
And then the change to the
Squashfs allows configuring a blocksize between 4KB and 1MB. The default is 128KB. Increasing blocksize, in general, increases compression efficiency at a cost of increased access time. Using 256KB for a blocksize appears to be a sweet spot balancing the two for gzip and zstd. Blocksize 512KB appears right for lzo. Gzip decreases by ~700KB. Lzo decreases by ~1.25MB. Zstd decreaes by ~2.5MB. Signed-off-by: Ian Leonard <firstname.lastname@example.org>