[xenpreview-dev] boot ine dom0_mem=memory

[Manzer, Kirk]

I have been using the dom0_mem parameter on the kernel for a while. I
limit dom0 to either 1 or 2 GB of memory depending on what the server is
doing, then I have no issues starting and domUs.  Prior to using
dom0_mem I was constantly having issues with starting domUs.


Kirk A. Manzer 
HP
TSG Solution Alliances, Linux
Phone: (281)-514-4979 
Cell: (832)-563-8120 
Fax: (281)-514-5802 
kirk.manzer at hp.com 


-----Original Message-----
From: xenpreview-dev-bounces at forge.novell.com
[mailto:xenpreview-dev-bounces at forge.novell.com] On Behalf Of
Jan.Albrecht at bertelsmann.de
Sent: Wednesday, May 09, 2007 12:30 PM
To: jbeulich at novell.com
Cc: xenpreview-dev at forge.novell.com
Subject: RE: [xenpreview-dev] boot ine dom0_mem=memory

My current xmtop output does look like this:

xentop - 19:26:43   Xen 3.0.4_13138-0.23_x
5 domains: 1 running, 4 blocked, 0 paused, 0 crashed, 0 dying, 0
shutdown
Mem: 7339416k total, 7337800k used, 1616k free    CPUs: 2 @ 1866MHz
NAME  STATE   CPU(sec) CPU(%)     MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%)
VCPUS NETS NETTX(k) NETRX(k) VBDS   VBD_OO   
3004 --b---       2522    1.0    1580928   21.5    1605632      21.9
1    2        0        0    4        0
3005 --b---      24691    1.0     270208    3.7     278528       3.8
1    2        0        0    2        0
3006 --b---     265829    1.8    1056640   14.4    1064960      14.5
1    2        0        0    3        0
3007 --b---       8178    1.8    1056640   14.4    1064960      14.5
1    2        0        0    3        0
Domain-0 -----r     181795   11.5    3217408   43.8   no limit       n/a
2    4  2168479   840665    0        0

As you can see I've 7GB for the whole server and 3,75GB for the domUs in
use. But xm top does only report 1616k free memory.
I've I do create an another domain on this server:
Will dom0 free some of it's mem to the new domain? If not the dom0_mem
parameter would make sense to me.

Jan

> -----Original Message-----
> From: Jan Beulich [mailto:jbeulich at novell.com] 
> Sent: Wednesday, May 09, 2007 3:10 PM
> To: Albrecht, Jan, NMI-DC
> Cc: xenpreview-dev at forge.novell.com
> Subject: Re: [xenpreview-dev] boot ine dom0_mem=memory
> 
> >is the line
> >dom0_mem=<memory size>
> >still useful?
> >I mean I've commented out this line and dom0 does take 3.2 GB of RAM,
> >which limits my domU a bit. If I do limit dom0 to lets say 
> 256MB, would
> >that make any difference?
>  
> If you want to avoid ballooning failures, the option may be 
> useful, but as
> long as your dom0 doesn't really allocate all that memory (so that the
> balloon driver can't grab it anymore) there should be no 
> problem omitting
> it. (256Mb for dom0 would be questionable at least - I'd 
> certainly not set it
> to this small a value.)
> 
> Jan
> 
> 
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