Re: RE: The caculation of the credit in credit_scheduler

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

On 11/10/10 03:39, Jiang, Yunhong wrote:
>
>
>> -----Original Message-----
>> From: George Dunlap [mailto:George.Dunlap@eu.citrix.com]
>> Sent: Tuesday, November 09, 2010 10:27 PM
>> To: Jiang, Yunhong
>> Cc: xen-devel@lists.xensource.com; 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.


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@ts.fujitsu.com
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html