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Re: [lorax] Split compression into separate methods; use xz to compress initrd



On 02/14/2011 10:05 AM, Will Woods wrote:
> xz compression makes the initrd 33% smaller (136M -> 90M).

Another 1.96MB can be squeezed from the kernel drivers (lib/modules/.../*.ko...).

>From a recent F15 alpha RC of install DVD:
10.608MB  tree of *.ko.gz-9
23.608MB  tree of *.ko
 8.984MB  tree of *.ko.xz-9
23.192MB  cpio *.ko
 7.022MB  (cpio *.ko).xz-9
11.236MB  tree of *.ko.gz-2

The 1.96MB is obtained from (8.98MB - 7.02MB).  Build the initrd
as the xz-compressed cpio archive containing the _uncompressed_ *.ko.
The kernel applies "xz -d", "cpio --extract", and "gzip -c -2",
getting a tree of *.ko.gz-2 that is (11.236MB - 10.608MB) = 0.628MB
larger than before, at a cost of about 1 second for re-compressing
while constructing the initramfs.  But in the meantime initrd.img
is about 2MB smaller.

-- 


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