On 07/01/2012 07:05 AM, Touko Korpela wrote: >> ... >> +if test "$post_2_6_38"; then >> + XZ="xz --check=crc32 -8" >> +else >> + XZ=false >> +fi > > From xz(1) manual page (you can ignore DecMem): > Preset DictSize CompCPU CompMem DecMem > -0 256 KiB 0 3 MiB 1 MiB > -1 1 MiB 1 9 MiB 2 MiB > -2 2 MiB 2 17 MiB 3 MiB > -3 4 MiB 3 32 MiB 5 MiB > -4 4 MiB 4 48 MiB 5 MiB > -5 8 MiB 5 94 MiB 9 MiB > -6 8 MiB 6 94 MiB 9 MiB > -7 16 MiB 6 186 MiB 17 MiB > -8 32 MiB 6 370 MiB 33 MiB > -9 64 MiB 6 674 MiB 65 MiB > > Better to use default setting "-6" that has lower memory requirement. >
Here is timing for re-compression from gzip to xz on Pegasos II with Freescale 7447 1GhZ processor and 1Gb RAM: set time compressed size -9 1m43.962s 9.5MB -8 1m44.824s 9.5MB -6 1m35.097s 9.6MB -3 1m10.080s 10.6MB -2 0m45.609s 10.7MB -0 0m19.286s 11.1MB I've originally decided to go with -8, mainly because the same preset is used in mkinitramfs form initramfs-tools package. It may be worth hearing arguments about the timing given that all presets currently produce vmlinuz smaller than the 12MB limit, but the compression time is very different. Milan
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