>-----Original Message-----
>From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Juergen Gross
>Sent: Wednesday, November 10, 2010 1:46 PM
>To: Jiang, Yunhong
>Cc: George Dunlap; xen-devel@xxxxxxxxxxxxxxxxxxx; Dong, Eddie; Zhang, Xiantao
>Subject: Re: [Xen-devel] RE: The caculation of the credit in credit_scheduler
>
>On 11/10/10 03:39, Jiang, Yunhong wrote:
>>
>>
>>> -----Original Message-----
>>> From: George Dunlap [mailto:George.Dunlap@xxxxxxxxxxxxx]
>>> Sent: Tuesday, November 09, 2010 10:27 PM
>>> To: Jiang, Yunhong
>>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Dong, Eddie; Zhang, Xiantao
>>> Subject: Re: The caculation of the credit in credit_scheduler
>>>
>>> On 05/11/10 07:06, Jiang, Yunhong wrote:
>>>> The reason is how the credit is caculated. Although the 3 HVM domains is
>pinned
>>> to 2 PCPU and share the 2 CPUs, they will all get 2* 300 credit when credit
>account.
>>> That means the I/O intensive HVM domain will never be under credit, thus it
>>> will
>>> preempt the CPU intensive whenever it is boost (i.e. after I/O access to
>>> QEMU),
>and
>>> it is set to be TS_UNDER only at the tick time, and then, boost again.
>>>
>>> I suspect that the real reason you're having trouble is that pinning and
>>> the credit mechanism don't work very well together. Instead of pinning,
>>> have you tried using the cpupools interface to make a 2-cpu pool to put
>>> the VMs into? That should allow the credit to be divided appropriately.
>>
>> I have a quick look in the code, and seems the cpu pool should not help on
>> such
>situation. The CPU poll only cares about the CPUs a domain can be scheduled,
>but
>not about the credit caculation.
>
>With cpupools you avoid the pinning. This will result in better credit
>calculation results.
My system is doing testing, so I can't do the experiment now, but I'm not sure
if the cpupool will help the credit caculation.
>From the code in csched_acct() at "common/sched_credit.c", the credit_fair is
>caculated as followed, and the creadt_fair's original value is caculated by
>sum all pcpu's credit, without considering the cpu poll.
credit_fair = ( ( credit_total
* sdom->weight
* sdom->active_vcpu_count )
+ (weight_total - 1)
) / weight_total;
Or did I missed anything?
Thanks
--jyh
>
>
>Juergen
>
>--
>Juergen Gross Principal Developer Operating Systems
>TSP ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967
>Fujitsu Technology Solutions e-mail: juergen.gross@xxxxxxxxxxxxxx
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>
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