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RE: [Xen-users] limit of domUs ?

To: "Yura Pismerov" <y.pismerov@xxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] limit of domUs ?
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Mon, 5 Jun 2006 17:12:54 +0200
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Thread-topic: [Xen-users] limit of domUs ?
What amount of memory have you given to Dom0? If Dom0 starts out with a
lot of memory, it's quite likely that it's not going to shrink to
"nothing" when more memory is needed by DomU's. 

As far as I'm aware, the number of domains should be limited only by the
available memory. 

However, there's also the Xen internal heap. It's default size is 12MB,
and it's not adjustable at run-time or by boot parameter[1]. I guess you
could change the source [.../xen/include/asm-x86/config.h:
XENHEAP_DEFAULT_MB - which is defined as DIRECTMAP_MBYTES, which is 12
in my version of the source code (fairly recent). 

[1] If you're running x86_64 or IA64 it IS adjustable, but not in 32-bit
kernel version. Don't ask me why that is... But Keir stated more than
once that they are not going to change the size of the heap, so I guess
it's that size for a good reason... If you're running x86_64/IA64, the
parameter to the kernel is xenheap_megabytes, and it takes an integer
number. 

--
Mats

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Yura Pismerov
> Sent: 05 June 2006 15:29
> To: 'xen-users@xxxxxxxxxxxxxxxxxxx'
> Subject: [Xen-users] limit of domUs ?
> 
> 
> What is the max number of domains one can create in Xen 3.0.2 ?
> For some reason, no matter what amount of RAM I allocate for 
> the domU's I can only create about 100 of them.
> After that I receive  "Error: (12, 'Cannot allocate 
> memory')", even though there is still plenty of free RAM available.
> Where should I look ?
> 
> 
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 


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