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

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

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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