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mreff555
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Joined: 10 Mar 2011
Posts: 169
Location: Philadelphia

PostPosted: Sun Oct 13, 2013 11:49 am    Post subject: lz4 questions Reply with quote

I'm upgrading to kernel 3.11.1 right now and I find myself overwhelmed by the urge to try lz4 compression on my kernel.
The problem is that I don't have lz4 compression installed and it's masked. Has anyone tried lz4 compression? why is it still masked?

Code:

mojo dan # emerge -av lz4

 * IMPORTANT: 9 news items need reading for repository 'gentoo'.
 * Use eselect news to read news items.


These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  N     ] dev-libs/apr-1.4.8-r1:1  USE="urandom -doc -older-kernels-compatibility -static-libs" 755 kB
[ebuild  N     ] dev-libs/apr-util-1.5.2:1  USE="berkdb gdbm ldap -doc -freetds -mysql -nss -odbc -openssl -postgres -sqlite -static-libs" 678 kB
[ebuild  N     ] dev-vcs/subversion-1.7.13  USE="berkdb dso nls python sasl webdav-neon -apache2 -ctypes-python -debug -doc -extras -gnome-keyring -java -kde -perl -ruby {-test} -vim-syntax -webdav-serf" PYTHON_TARGETS="python2_7 -python2_6" 5,903 kB
[ebuild  N    *] app-arch/lz4-9999  0 kB

Total: 4 packages (4 new), Size of downloads: 7,335 kB

The following keyword changes are necessary to proceed:
 (see "package.accept_keywords" in the portage(5) man page for more details)
# required by lz4 (argument)
=app-arch/lz4-9999 **

NOTE: The --autounmask-keep-masks option will prevent emerge
      from creating package.unmask or ** keyword changes.

Use --autounmask-write to write changes to config files (honoring
CONFIG_PROTECT). Carefully examine the list of proposed changes,
paying special attention to mask or keyword changes that may expose
experimental or unstable packages.
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frostschutz
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Joined: 22 Feb 2005
Posts: 2424
Location: Germany

PostPosted: Sun Oct 13, 2013 1:53 pm    Post subject: Reply with quote

Do you need to emerge lz4 in order to use lz4 compression in the kernel?

The kernel packs lz4 code itself, seeing as how it wouldn't be able to decompress itself at boot otherwise.

The only difference (if any) is the size of the kernel image and/or boot time should lz4 decompression be slightly faster than whatever you're using now. For most desktops/laptops etc. this means there is absolutely no reason to switch. The system won't run any faster/different because of it.

I still use the good old bzImage ...
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mreff555
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Joined: 10 Mar 2011
Posts: 169
Location: Philadelphia

PostPosted: Sun Oct 13, 2013 3:00 pm    Post subject: Reply with quote

Quote:

I still use the good old bzImage ...


I've never been very good at leaving something alone. I've gone through all the others and currently prefer xz because of its combination of speed and compression. However, when I saw lz4's speed compared to even b2z compression speed I had to give it a try.

I tried it about a month ago, when 3.11.1 was still masked and the kernel wouldn't extract. I tried it again, it does work, however it isn't all that impressive.

Using lz4 as opposed to xz only increased the compressed kernel by 0.1mb, but there wasn't really much of an increase in speed. Oh well, it least it isn't broken

Code:

-rw-r--r-- 1 root root  512 Jul  7 13:15 boot.0800
-rw-r--r-- 1 root root  512 Sep  6 20:18 boot.0810
-rw-r--r-- 1 root root  79K Oct 13 08:10 config.kernel-3.11.1-gentoo-r00
-rw-r--r-- 1 root root  11M Oct 13 10:55 kernel-3.10.0-gentoo.tar.xz
-rw-r--r-- 1 root root  11M Aug 17 18:29 kernel-3.10.3-gentoo.tar.xz
-rw-r--r-- 1 root root 3.1M Aug 30 20:31 kernel-3.10.4-gentoo.tar.xz
-rw-r--r-- 1 root root 3.1M Aug 30 20:35 kernel-3.10.6-gentoo.tar.xz
-rw-r--r-- 1 root root 3.2M Oct 13 08:11 kernel-3.11.1-gentoo-r00
-rw-r--r-- 1 root root  15M Aug 17 18:26 kernel-3.8.13-gentoo.tar.xz
-rw------- 1 root root 151K Oct 13 08:13 map

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