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RE: [Xen-users] priority of dom0?


  • To: "Sven Köhler" <skoehler@xxxxxx>
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Fri, 3 Nov 2006 17:22:12 +0100
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 03 Nov 2006 08:23:10 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: Acb/YsEaBhtbpTeGQO+qdoqlHdzywAAAMW3g
  • Thread-topic: [Xen-users] priority of dom0?

 

> -----Original Message-----
> From: Sven Köhler [mailto:skoehler@xxxxxx] 
> Sent: 03 November 2006 16:11
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] priority of dom0?
> 
> >> when i compile something in dom0, my domUs are more then 
> >> unresponsible.
> >> Any clue, what's going on? How can i change the "priority" 
> of dom0? I
> >> think, that the CPU-time should be equally distributed 
> >> between the dom0
> >> and the domUs.
> > 
> > Whilst you can do this, the risk is that you get other 
> problems if you do that (like one DomU running away and Dom0 
> not getting a chance to run instead :-( which is slightly 
> worse, in case you would like to for example KILL that 
> DomU!)...  You also want Dom0 to have a high priority (or to 
> be able to run for as long as it needs) to be able to 
> correctly and quickly respond to IO requests made on behalf 
> of DomU's. Unfortunately, this counteracts the Dom0 being low 
> priority...
> 
> Well, i would expect some "fairness", that is:
> 
>   50% dom0, 50% domU
> or
>   33% dom0 and 66% for two domUs
> or
>   25% dom0 and 75% for three domUs
> and so on ...
> 
> Perhaps, people would also like to say: guarantee up to 33% 
> percent CPU
> usage to dom0. (Not meaning, that dom0 is limited to 33% and 
> not meaning
> that all domUs together are limited to 66%)
> 
> Don't you think, that this would be enough to ensure that IO 
> and network
> is working properly?
> 
> Of course, that requires a (fairly simple?) scheduler within Xen.

That is what the credit scheduler is supposed to do... What version of Xen are 
you using?

What does it say if you do "xm dmesg | grep -i sched"?

--
Mats



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