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

[Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>]

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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