Re: [Xen-users] cpu_weight and cpu_cap

["Dylan Martin" <dmartin@xxxxxxxxxxxxxxxxxx>]

I found some real documentation!

http://wiki.xensource.com/xenwiki/Scheduling
http://wiki.xensource.com/xenwiki/CreditScheduler

But I still don't know what I should do...

I have a VM that's a production web server and another that's a development
web server used by students.  I expect the students to occasionally do
something silly that tries to use all the available processor.  If the student
dev machine grinds to a halt, it's no big deal.  If the production web server
gets sluggish, it's a real problem.  Also, I'd like the student server to be
able to use as much CPU as the production server isn't using.

It looks like cpu_cap wouldn't be good because it would prevent the student
dev VM from using all the available CPU when the production VM is idle.  Maybe
cpu_weight is what I want?

If I did a weighting like:

production = 1000
dev        = 10

Then when both machines are asking for processor at the same time, production
would get 10 times as much, but if only dev was asking for processor, it could
take as much as it wanted.  That looks closer to what I want.

So, er, I guess my question now is, am I right, or am I totally crazy and this
would make bad things happen?

Thanks
-Dylan


On Feb 1, 2008 4:30 PM, Todd Deshane <deshantm@xxxxxxxxx> wrote:
>
>
>
> On Feb 1, 2008 2:46 PM, Dylan Martin <dmartin@xxxxxxxxxxxx> wrote:
> > I just did a search for 'cpu_cap' and another for 'cpu_weight' in the
> > list archives and got zero results.  Weird.
> >
> > Anyway, I have a PV VM that might try and use too many resources.  How
> > can I use 'cpu_cap' and 'cpu_weight' to control that?  Is there any
> > sort of reference doc that describes these settings?  Maybe examples?
> > I can kindof guess what cpu_cap does, but cpu_weight could mean
> > anything.
> >
>
> Something to look at:
>
> Usage: xm sched-credit -d <Domain> [-w[=WEIGHT]|-c[=CAP]]
>
> Get/set credit scheduler parameters.
>   -d DOMAIN, --domain=DOMAIN     Domain to modify
>   -w WEIGHT, --weight=WEIGHT     Weight (int)
>   -c CAP, --cap=CAP              Cap (int)
>
>
> >
> >
> > OR!
> >
> > If there is a better way to manage VM prioritisation, please let me
> > know.  Or even more generally, any best practices to keep a VM from
> > making other VMS too sluggish?
> >
> > Thanks!
> > -Dylan
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> >
>
>

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