RE: [Xen-users] Maximal RAM reservation for Linux-Dom0

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

Well, the Xen kernel itself will use some memory, and there may be
"holes" in the memory too (for example for ISA/BIOS space just under
1MB), so if you've got 512MB of memory in your machine, I don't expect
you to be able to give 512MB to the Dom0. 

I'm not sure how much memory the Xen kernel uses, the code in the kernel
itself is about 3-400KB, 24KB of initialized data and 128KB of BSS, so a
good half a megabyte, but it will also allocate/reserve some other
memory areas, which I'm sure will amount to a fair bit more. For
instance, in the mm.c, there's a single allocation of 4MB for a
"mapcache". There are also many small allocations through xmalloc, that
build up to some amount of memory usage. How big that is, I can't really
estimate, because it's too many places to easily and quickly understand
what gets run how many times, etc. 

--
Mats
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Subhabrata Bhattacharya
> Sent: 10 August 2005 10:20
> To: Jean-Christophe Guillain
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Maximal RAM reservation for Linux-Dom0
> 
> > > If you don't intend to run any guest domains on the host, 
> I don't see why  you can't use your whole memory for dom0...
> 
> I don't see the reason too but on allocation, I find Xen 
> Domain 0 spitting up cannot allocate enough memory for Domain 
> 0 reservation [something of that sort]
> 
> > > But why do you want to use an Xen kernel in this case ?
> 
> Just out of curiosity :)
> 
> 
> > But I think that it would be interesting to know how to 
> calculate the amount of memory we can't allocate to any 
> domain when we have several ones running (xen0 + xenUs)...
> > What it depends on ?
> 
> Yeah I jibe with this.
> 
> ~$ubh
> 
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> 


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