On Wed, Mar 16, 2011 at 20:12, KESHAV P.R. wrote:

On Wed, Mar 16, 2011 at 20:09, Gaetan Bisson wrote:

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[2011-03-16 19:58:23 +0530] KESHAV P.R.:

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Now that kernel 2.6.38 supports xz (lzma2, not lzma), how about using it as the default compression for the kernel and initramfs. mkinitcpio simply requires COMPRESSION="xz" to generate lzma2 compressed initramfs. But xz compressed kernel requires change in the config option and once module-init-toools supports xz compressed modules we can say good bye to gzip.

mkinitcpio.conf requires COMPRESSION="xz --check=crc32" , not simply "xz" since crc64 (default) checksum is not supported by kernel de-compressor. See http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Do... . - Keshav

On Wed, Mar 16, 2011 at 22:42, Thomas Bächler wrote:

Am 16.03.2011 17:12, schrieb KESHAV P.R.:

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On Wed, Mar 16, 2011 at 20:12, KESHAV P.R. wrote:

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On Wed, Mar 16, 2011 at 20:09, Gaetan Bisson wrote:

...

[2011-03-16 19:58:23 +0530] KESHAV P.R.:

...

Now that kernel 2.6.38 supports xz (lzma2, not lzma), how about using it as the default compression for the kernel and initramfs. mkinitcpio simply requires COMPRESSION="xz" to generate lzma2 compressed initramfs. But xz compressed kernel requires change in the config option and once module-init-toools supports xz compressed modules we can say good bye to gzip.

mkinitcpio.conf requires COMPRESSION="xz --check=crc32" , not simply "xz" since crc64 (default) checksum is not supported by kernel de-compressor. See http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Do...

Thanks for this info. There is one request to remove the "-9" default compression ratio, so this is probably a good time to change how compression is handled for mkinitcpio. The advantage of xz over lzma shouldn't be that big in any case.

Kernel documentation recommends using a 1MiB dictionary max (for the kernel, maybe more for initramfs), not 64MiB that is required for -9 option. Otherwise it is better to have specific compression level option for each format in mkinitcpio.conf instead of the actual mkinitcpio script. In case of xz, kernel docs recommends I am typing this from Arch x86_64 2.6.38 with xz --check=crc32 -9 compressed initramfs. I don't know about any problems with -9 option, except maaybe amount of memory required to decompress. - Keshav Offnote: What happened to Big Kernel Lock (in the config)

On Wed, Mar 16, 2011 at 11:14 PM, Thomas Bächler wrote:

There are patches that allow the BKL to be removed in 2.6.39 I think. We'll see.

The BKL will no longer be there in .39: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=.... Cheers, Tom