Messages in this thread | | | Date | Fri, 01 Feb 2013 16:13:40 +0900 | From | "kyungsik.lee" <> | Subject | Re: [RFC PATCH 0/4] Add support for LZ4-compressed kernels |
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On 2013-01-30 오전 7:55, David Sterba wrote: > On Sat, Jan 26, 2013 at 02:50:43PM +0900, Kyungsik Lee wrote: >> This patchset is for supporting LZ4 compressed kernel and initial ramdisk on >> the x86 and ARM architectures. > Have you considered the 'high compression' mode of lz4? > http://code.google.com/p/lz4/source/browse/trunk/lz4hc.c > > The compression format remains the same, the compressor tries harder > (but is slower), resulting compression ratio is better. > > an examle compression for vmlinux.bin of x86_64 build: > > input size: 16509520 bytes > > lz4 (svn 88): > output size: 6393684 (38.7%) > compression time: 41.7 ms (395 MB/s) > decompression time: 13.7 ms (1204 MB/s) > > lz4hc (svn 88): > output size: 5319137 (32.2%) > compression time: 683 ms (24 MB/s) > decompression time: 13.1 ms (1259 MB/s) > > compressed file delta: 6393684 - 5319137 = 1074547 ~ 1MB > > tested on a Nehalem box; same test on my slow desktop gives > > lz4: > compression time: 97 ms (169 MB/s) > decompression time: 25.7 ms (643 MB/s) > > lz4hc: > compression time: 1386 ms (11 MB/s) > decompression time: 26 ms (619 MB/s) > > While the decompression time is almost the same, image size is smaller. > The kernel image compression is run in userspace and the low speed is > not much of concern for a one-time operation. > > For the reference, lzo (current kernel version) run on the destktop: > > output size: 6026256 (36.5%) > decompression time: 79.6 ms (207 MB/s) > >> It seems that it’s worth trying LZ4 compressed kernel image or ramdisk >> for making the kernel boot more faster. > There's another potential user of lz4: btrfs. I've submitted a feature > preview integrating lz4 compression > http://thread.gmane.org/gmane.comp.file-systems.btrfs/15744 > and we have tried to integrate the HC mode as well > http://thread.gmane.org/gmane.comp.file-systems.btrfs/18165 > . > So far it's on a slow track, conceptually it works, but I the code needs > some work so it could live under lib/* (we've used the svn sources > with minor changes, no kernel coding style). It would be easier for me > to enhance the existing lib/lz4/* codebase. > > Also zram could consider lz4, I'm not sure if there are other potential > users. Yes, I guess squash fs and crypto would also benefit from lz4.
Thanks, Kyungsik
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