Mailinglist Archive: opensuse-kernel (148 mails)

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Re: [opensuse-kernel] Squashfs
  • From: Greg KH <gregkh@xxxxxxx>
  • Date: Wed, 14 Jan 2009 13:28:16 -0800
  • Message-id: <20090114212816.GA22345@xxxxxxx>
On Wed, Jan 14, 2009 at 03:12:32PM -0600, Matt Sealey wrote:
I just noticed that while squashfs 3.4 kernel module is used on the
-default kernel, the squashfs tools on both PowerPC and x86 repos are stuck
at 3.2

neko@frodo:~> mksquashfs -version
mksquashfs version 3.2-r2 (2007/01/15)

Is there any particular reason for this? Is there an update planned?

Someone needs to kick the owner of the userspace squashfs tools to get
them to update them. If you could be so kind as to file a bug against
the package, that would help.

Also, more for the kernel guys.. is there any reason why the mkinitrd etc.
stuff relies on cpio archives when the SUSE kernel is built with squashfs
(granted as a module), all the rescue/install images are squashfs?

No specific reason, other than "that's just the way we've always done
it."

Do you really want to touch that mkinitrd code to change this? :)

It does not provide any remarkably better compression - in fact I tested
100k larger filesystem with mksquashfs 3.2 but then mksquashfs 3.2 refuses
to use large block sizes so the compression is lower than it could be, also
mksquashfs 3.4 supposes a 10% improvement and unsquashfs supposes a 40%
improvement in speed in creation and extraction (we will ignore the kernel
improvements as, they are in the kernel already)..

.. But a few tests in performance usually always show that accessing a
squashfs initrd mounted to RAM is faster than a cpio initrd in RAM.

Are you sure? What kind of performance difference is there?

It also has a few extra little advantages here and there but I do not
know if they are worth it, but I do know that managing squashfs
filesystems is a billion times easier than pushing cpio archives
around.

But these are generated "on-the-fly" and don't need to be managed by
anything, right?

What advantages do you know of?

Since squashfs is going to be in the kernel mainline at some point (it's in
Linus' tree)

Yes, it will be in 2.6.29, and is already there in 2.6.29-rc1.

and everyone and his dog makes squashfs initrds,

Who else?

are we going to see a move to it at some point and have the thing
built in with more use of the format?

I think the goal with mkinitrd is to work with the community to come up
with a common tool that all the distros use. Dave Jones is currently
working on a first cut at this, and then we will all get together to go
from there. If it happens to use squashfs instead of cpio, well, that
will be up to the community, not just us.

thanks,

greg k-h
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