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

Hi, Emmanuel

Sorry for mis-reading it.

The measured value to omit 2 SPIN DomU is same as w/ 2SPIN DomU.



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 % ) 

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.
>#vcpu(s)=2(no 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.
>Atsushi SAKAI
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