Pkg xen devel - Dec 2006 - Re: Bug#390862: -bigmem version of xen kernels is really needed

What about idea not to *add* pae versions of xen kernels, but to *replace* 
non-pae versions with pae versions?

Rationale:

- not increase in archive size or linux-2.6 package build time,

- this will improve compatimility with other distros (consider scenario 
when running FC or RHEL in domU; these distros do ship only pae xen 
kernels, according to 
http://lists.alioth.debian.org/pipermail/pkg-xen-devel/2006-December/000998.html)

- pae kernels are ok for any x86 machines; slowdown caused by enabling pae 
on machines with less than 3.%G of memory, if any at all, is hardly 
measurable on machines where using xen makes sence (anyone using xen on 
Pentium-I with 128M of ram?)

Nikita V. Youshchenko wrote:
> What about idea not to *add* pae versions of xen kernels, but to *replace* 
> non-pae versions with pae versions?
Hear, hear!!!

Sincerely,

Jan.

On Tue, Dec 12, 2006 at 12:54:31PM +0300, Nikita V. Youshchenko
wrote:
> 
> What about idea not to *add* pae versions of xen kernels, but to *replace* 
> non-pae versions with pae versions?
> 
> Rationale:
> 
> - not increase in archive size or linux-2.6 package build time,
> 
> - this will improve compatimility with other distros (consider scenario 
> when running FC or RHEL in domU; these distros do ship only pae xen 
> kernels, according to 
>
http://lists.alioth.debian.org/pipermail/pkg-xen-devel/2006-December/000998.html)
>
http://fedoraproject.org/wiki/FedoraXenQuickstartFC6

"Any x86_64, or ia64 CPU is supported for running para-virtualized guests.
To run i386 guests requires a CPU with the PAE extension."

So FC6 is PAE only, and latest update to FC5 also switched to PAE xen
kernel.

RHEL5 will be PAE only too.

I don't know what Suse uses..

-- Pasi
 
> - pae kernels are ok for any x86 machines; slowdown caused by enabling pae 
> on machines with less than 3.%G of memory, if any at all, is hardly 
> measurable on machines where using xen makes sence (anyone using xen on 
> Pentium-I with 128M of ram?)
>

Am Dienstag, 12. Dezember 2006 10:54 schrieb Nikita V.
Youshchenko:
> What about idea not to *add* pae versions of xen kernels, but to *replace*
> non-pae versions with pae versions?
I don't think that debian should ship only pae-enabled kernels, because this
has some disadvantages:

- the slowdown, even if it's minimal, I personaly don't want to get
forced to
use it.

- only pae-enabled system can use xen in 32bit mode, cpu's without pae
cannot
use xen at all! Not every cpu/bios is able to handle pae. 
(see "cat /proc/cpuinfo" for your cpu and check your bios settings if
you are
not sure).

- I had some trouble with pae on standard server hardware (in combination with 
xen) in the past. I think pae can make your system less stable (in rare 
cases).

My personal conclussion: pae is only a dirty hack. use it if you must, 
otherwise a non pae-enabled kernel/os is better.

I think debian should normal AND pae-enabled kernels, or maybe have the kernel 
decice that on boottime automaticly (if that's possible).

ah, and I don't get the "distribution compatibiltiy" point.
If your domU system is debian based, then you will use the non-pae kernel from 
etch and all your domUs also can use the same kernel. It doesn't matter if 
domU is also debian or fedora or something else, they should work with a 
debian kernel...
The same is true for a dom0 based on fedora and debian as domU. Use the same 
kernel (the one that gets shipped with the dom0 distribution) and use that 
for your debian domUs, too.

For compatibility it's more important that every distribution uses udev (for
example) and not the depricated hotplug system.

just my 5 cent ;-P

--Ralph