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

[Emmanuel Ackaouy <ack@xensource.com>]

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.

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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> >
> 
> 
> 
> 
>