On 07/02/2012 07:07 AM, Touko Korpela wrote: > On Sun, Jul 01, 2012 at 11:03:02AM -0400, Milan Kupcevic wrote: >> 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: > > Use of -8 option isn't a good thing for systems having only 512 Mib or less > memory. This operation shouldn't force to use slow swap space or OOM. > >> >> 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. > > Your size numbers show that -8 produces only marginally smaller images. > If mkinitramfs (initramfs-tools) uses -8 for xz compression, it should be > changed too. >
You are right. I just did two more runs with -4 and -5: set time compressed size -5 1m28.009s 9.6MB -4 1m12.628s 9.8MB Compression time goes up while compression gain gets insignificant with presets larger than -4. It is probably best to go with -4. It is time efficient and needs only 48 MiB for compression. Installer will be able to finish on EFIKA 5200B boards with 128MB built-in memory. Milan
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