RE: [Xen-users] Improve performance of domain U

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Hans de Hartog
> Sent: 03 September 2006 13:30
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Improve performance of domain U
> 
> Hi,
> 
> Somewhere earlier in this thread, naha wrote
> that he had 1 kernel for all domains.
> I understood that the kernelconfigurations for
> dom0 and domU must be different (backend stuff
> for dom0 and frontend stuff for domU).
> If both are included, could that lead to bad
> performance?

Not particularly noticable in any system that has a reasonable amount of
memory per domain. If you're trying (as I've seen examples of) to cram
32 domains into 256 MB of memory, you WILL need to strip anything that
isn't absolutely critical out of the kernel. 

But driver that are modules will not use any memory anyway (diskspace
will be used, but no memory as such), so if you have modules in the
kernel (most people will build this way), then surplus drivers will
never get loaded, and thus not consume any resource. 

The backend/frontend choice is done all automagically based on the
domain's "plug-n-play" mechanisms, so it will not load any of the
frontend drivers when it need backend drivers or the other way around.

Obviously, if the front/back-end drivers are compiled in fixed into the
kernel, a small amount of extra space is needed for the kernel, but I
doubt that it's more than 100K or so, and if we're still talking about
"normal" systems where there goal is to have several megabytes per
domain, it would make no noticable differnce. 

--
Mats
> 
> Thanks,
> Hans.
> 
> 
> 
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