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xen-users
Re: [Xen-users] Smaller kernel for DomU ?
But... I don't see "vmx" in my /proc/cpuinfo :
flags : fpu de tsc msr pae cx8 apic sep mtrr cmov pat clflush
acpi mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc rep_good pni
ssse3 cx16 sse4_1 lahf_lm
and :
root ! granite:~# xm dmesg | grep VMX
(XEN) CPU0: VMX disabled by BIOS.
(XEN) VMX: failed to initialise.
So VT is not used... maybe I should enable it ;)
Olivier
Olivier B. a écrit :
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
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