Re: [Xen-devel] [PATCH 1 of 3] Support of getting scheduler defaults

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

On 05/22/2012 02:32 PM, Ian Campbell wrote:
> On Tue, 2012-05-22 at 13:29 +0100, Juergen Gross wrote:
> > On 05/22/2012 02:22 PM, Ian Campbell wrote:
> > > On Tue, 2012-05-22 at 10:16 +0100, Juergen Gross wrote:
> > > > Support a new sysctl schedop sub-command to get the scheduling defaults of a
> > > > specific scheduler.
> > > Why is XEN_DOMCTL_SCHEDOP_getinfo not sufficient here?
> > >
> > > Isn't it actually more useful/meaningful to get the current actual
> > > setting rather than a default?
> > When setting the parameters from the config file we have no domain yet which
> > we would have to specify for XEN_DOMCTL_SCHEDOP_getinfo. I didn't want to
> > parse part of the config only after domain creation.
> That seems like another problem with doing this up front instead of
> doing read-modify-write when we come to set the values for the domain.
Do you think it would be okay to parse the scheduler config data _after_
domain creation? If yes, the read-modify-write approach is simple and always
correct. If no, you will have to initialize the parameters to something
scheduler specific, and not domain specific.

> > A default should be okay, as this is what we want to modify. :-)
> > The scheduler should initialize a new domain with this default, of course.
> So I can't use this interface to change the current one of the current
> settings for running a domain, while leaving the others at their current
> value?
I don't understand this sentence :-) ...

> Which interface can I use for that and why isn't it the same as this
> one?
... making it hard to answer to this one. :-)
Nevertheless trying: you can change the scheduling parameters of a running
domain with xl sched-credit/sched-sedf/...


Juergen

--
Juergen Gross                 Principal Developer Operating Systems
PDG ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
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