xz compression makes the initrd 33% smaller (136M -> 90M). The extra
memory overhead at decompression time is negligible: testing showed
that any system with enough RAM to use the gzip-compressed initrd was
also able to load the xz-compressed initrd with no trouble.

Note that '--check=crc32' is needed because the kernel doesn't know
how to perform the default xz integrity check (crc64).
---
src/pylorax/constants.py | 2 ++
src/pylorax/installtree.py | 24 ++++++++++++------------
2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/src/pylorax/constants.py b/src/pylorax/constants.py
index 547a938..4967450 100644
--- a/src/pylorax/constants.py
+++ b/src/pylorax/constants.py
@@ -41,6 +41,7 @@ class LoraxRequiredCommands(dict):
self["DMSETUP"] = "dmsetup"
self["FIND"] = "find"
self["GCONFTOOL"] = "gconftool-2"
+ self["GZIP"] = "gzip"
self["IMPLANTISOMD5"] = "implantisomd5"
self["ISOHYBRID"] = "isohybrid"
self["LDCONFIG"] = "ldconfig"
@@ -52,6 +53,7 @@ class LoraxRequiredCommands(dict):
self["MOUNT"] = "mount"
self["PARTED"] = "parted"
self["UMOUNT"] = "umount"
+ self["XZ"] = "xz"

def __getattr__(self, attr):
return self[attr]
diff --git a/src/pylorax/installtree.py b/src/pylorax/installtree.py
index 9883bba..e1a0bdb 100644
--- a/src/pylorax/installtree.py
+++ b/src/pylorax/installtree.py
@@ -25,7 +25,6 @@ logger = logging.getLogger("pylorax.installtree")
import sys
import os
import shutil
-import gzip
import re
import glob
import time
@@ -49,6 +48,14 @@ class LoraxInstallTree(BaseLoraxClass):

self.lcmds = constants.LoraxRequiredCommands()

+ def compress_initrd_pipe(self, stdin, stdout):
+ return subprocess.Popen([self.lcmds.XZ, '--check=crc32', '-9', '-c'],
+ stdin=stdin, stdout=stdout)
+
+ def compress_module(self, filename):
+ return subprocess.call([self.lcmds.GZIP, '-9', '-f',
+ filename])
+
def remove_locales(self):
chroot = lambda: os.chroot(self.root)

@@ -310,14 +317,7 @@ class LoraxInstallTree(BaseLoraxClass):
for root, _, fnames in os.walk(moddir):
for fname in filter(lambda f: f.endswith(".ko"), fnames):
path = os.path.join(root, fname)
- with open(path, "rb") as fobj:
- data = fobj.read()
-
- gzipped = gzip.open("{0}.gz".format(path), "wb")
- gzipped.write(data)
- gzipped.close()
-
- os.unlink(path)
+ self.compress_module(path)

def run_depmod(self, kernel):
systemmap = "System.map-{0.version}".format(kernel)
@@ -521,9 +521,9 @@ class LoraxInstallTree(BaseLoraxClass):
stdin=find.stdout, stdout=subprocess.PIPE,
preexec_fn=chdir)

- gzipped = gzip.open(initrd.fpath, "wb")
- gzipped.write(cpio.stdout.read())
- gzipped.close()
+ compress = self.compress_initrd_pipe(stdin=cpio.stdout,
+ stdout=open(initrd.fpath,"wb"))
+ compress.communicate()

# move modules out of the tree again
shutil.move(joinpaths(self.root, "modules", kernel.version),
--
1.7.4

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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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