Re: [Xen-devel] [Q] about Credit Scheduler Dom0 Scheduling policy.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Oct 26, 2006 at 09:42:11AM +0100, Emmanuel Ackaouy wrote:
> Thanks.
> 
> That indicates the dom0 and I/O generating domU are preempting
> the spinners but not each other and are therefore running
> optimally.
> 
> That is great news.
> 

Is this patch going to be submitted for 3.0.3-1 or only for unstable (3.0.4)? 

-- Pasi

> On Thu, Oct 26, 2006 at 05:35:20PM +0900, Atsushi SAKAI wrote:
> > Hi, Emmanuel
> > 
> > Sorry for mis-reading it.
> > 
> > The measured value to omit 2 SPIN DomU is same as w/ 2SPIN DomU.
> > 
> > Result 
> > 
> >  44
> > 133
> > 533
> > (Kbps)
> > 
> > And xentop says 
> > the CPU usage for Dom0 DomU3 is same as w/ 2 SPIN DomU
> > (Both Dom0 and DomU3 usages are 1.0 to 1.2 % ) 
> > 
> > Thanks,
> > Atsushi SAKAI
> > 
> > >The bench mark is same as previous one.
> > >
> > >Only Dom0 and DomU3 are no spinning vcpus.
> > >Other DomU1 and DomU2 are spinning vcpus.
> > >
> > >#pcpu(s)=1
> > >#vcpu(s)=2(no spinning)
> > >#vcpu(s)=2(spinning)
> > >#vcpu(s)=4(total spinning and no spinning)
> > >
> > >>
> > >>Out of curiosity, what are the numbers like when running this
> > >>benchmark with no spinning VCPUs competing?
> > >>
> > >>> With this patches, the CREDIT scheduler changed for I/O aware.
> > >>> (At vcpu_wake, the priority changes from UNDER to BOOST,
> > >>> At vcpu_acct, the priority changes from BOOST to UNDER.) 
> > >>> 
> > >>> It seems reasonable fixes!
> > >>> But I am afraid many I/O intensive GuestOSes are running.
> > >>> (I hope this prospect is needless fear.)
> > >>
> > >>I've been careful to prevent BOOSTed VCPUs from taking over the
> > >>system or otherwise impacting fairness:
> > >>
> > >>- Only VCPUs with positive credits can be boosted.
> > >>- While boosted, a VCPU is charged for any substential CPU
> > >>  resources consumed.
> > >>- VCPUs can run uninterrupted with a boosted priority for no
> > >>  more than 10ms (1/3-rd of a full time slice).
> > >>
> > >>Only VCPUs which consume a negligeable amount of CPU resources
> > >>should get real benefit from boosting. When multiple VCPUs are
> > >>boosted, they will round robin or be queued FIFO. The idea is
> > >>for a boosted VCPU to preempt spinners but not other boosted
> > >>I/O intensive guests. A VCPU cannot use the boosting mechanism
> > >>to consume more CPU than its allocated fair share.
> > >
> > >I agree.
> > >
> > >Thanks
> > >Atsushi SAKAI
> > >
> > >
> > >
> > >

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