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

["Olivier B." <xen.list@xxxxxxxxx>]

Hi,

thanks ;) The host is an Intel Xeon X3350, running a Debian Lenny 
64bits. I use on it the package "xen-hypervisor-3.2-1-amd64" from Debian 
and kernel "linux-image-2.6.26-1-xen-amd64" from Debian too.
For the DomU, it was running the same Debian kernel, but I change it for 
a "home made" vanilla Kernel 2.6.28.6 (to can use the last version of 
ext4) :
the config : http://apt.daevel.fr:9999/daevel/config-2.6.28.N-dae-xen
the kernel : 
http://apt.daevel.fr:9999/daevel/linux-image-2.6.28.6-dae-xen_1.0_amd64.deb
And the diff for .config with my "normal" kernel :
daevel@may:~/linux$ diff config-2.6.28.N-dae-core2 config-2.6.28.N-dae-xen
160c160
< # CONFIG_FREEZER is not set
---
> CONFIG_FREEZER=y
177c177,184
< # CONFIG_PARAVIRT_GUEST is not set
---
> CONFIG_PARAVIRT_GUEST=y
> CONFIG_XEN=y
> CONFIG_XEN_MAX_DOMAIN_MEMORY=4
> CONFIG_XEN_SAVE_RESTORE=y
> # CONFIG_KVM_CLOCK is not set
> # CONFIG_KVM_GUEST is not set
> CONFIG_PARAVIRT=y
> CONFIG_PARAVIRT_CLOCK=y
294c301
< # CONFIG_HOTPLUG_CPU is not set
---
> CONFIG_HOTPLUG_CPU=y
304a312,313
> CONFIG_PM_SLEEP_SMP=y
> CONFIG_PM_SLEEP=y
317a327
> CONFIG_ACPI_HOTPLUG_CPU=y
329c339
< # CONFIG_ACPI_CONTAINER is not set
---
> CONFIG_ACPI_CONTAINER=m
663a674
> CONFIG_XEN_BLKDEV_FRONTEND=y
1040a1052
> CONFIG_XEN_NETDEV_FRONTEND=y
1140a1153,1155
> CONFIG_HVC_DRIVER=y
> CONFIG_HVC_IRQ=y
> CONFIG_HVC_XEN=y
1482a1498,1499
> CONFIG_XEN_BALLOON=y
> CONFIG_XEN_SCRUB_PAGES=y
1814c1831,1834
< # CONFIG_VIRTUALIZATION is not set
---
> CONFIG_VIRTUALIZATION=y
> # CONFIG_KVM is not set
> # CONFIG_VIRTIO_PCI is not set
> # CONFIG_VIRTIO_BALLOON is not set

I hope this will help.

Thanks for your advise. I want to limit "overhead" or "memory 
consuption" on DomU, but if I well understand you, there is not a big 
difference.
So for simplicity I think I will add the required Xen options on my 
common kernel.
For LVM, in fact I was not thinking we can use it directly from DomU ;)

Thanks again,
Olivier

Fajar A. Nugraha a écrit :
> 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
> > 2.6.28.6 version (amd64). It seems to work very well (ext4 !), but should I
> >     
> Congratulations!
> Can you share your setup? It IS a pv domU, right?
> I tried 2.6.28.6 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.
>
> Regards,
>
> Fajar
>   

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users