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Re: [Xen-users] Smaller kernel for DomU ?

To: "Olivier B." <xen.list@xxxxxxxxx>
Subject: Re: [Xen-users] Smaller kernel for DomU ?
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Sat, 21 Feb 2009 19:19:07 +0700
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On Fri, Feb 20, 2009 at 11:02 PM, Olivier B. <xen.list@xxxxxxxxx> wrote:
> Hello,
> On a DomU I've just replaced the Debian's 2.6.26 kernel by a Vanilly
> version (amd64). It seems to work very well (ext4 !), but should I

Can you share your setup? It IS a pv domU, right?
I tried as domU kernel, and only able to get it working as
32bit PAE domU. 64bit domU doesn't work. Can you share :
- what Xen version you use and from where (debian or vanilla xen.org)
- what is your domU kernel .config

> reduce the size of the kernel ?
> For example, since the DomU use the "noop" scheduler, I can remove
> anticipatory, deadline, and cfq from my kernel, no ? And... is there any
> interest to do that ?
> Also the Dom0 use software raid and LVM, can I remove that support in DomU ?

Depends on what you're trying to do. If you want it to be "easy", it
should be as similar as possible as your domU distros' vendor kernel.
However if all your domU has the same kernel requirements (for
example: all of them uses ext4 and none of them needs iptables) it
might be beneficial to have a specialized kernel with all needed
features built-in.

Some "features" can be built as module anyway, so having them would allow
- easy loading when needed
- taking very little or no resource when not loaded

As for LVM on domU, as of now it is the only way to be able to extend
domU's storage online (using xm block-attach and extending domU's VG).
If you don't need to extend storage online (i.e. you can afford
rebooting domU to add storage) then you can safely remove, but IMHO
the space and memory savings will be somewhat insignificant.



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