Re: [Xen-devel] [BUG] mistakenly wake in Xen's credit scheduler

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Wed, Oct 28, 2015 at 6:08 AM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> On Wed, 2015-10-28 at 07:01 +0100, Juergen Gross wrote:
>> On 10/28/2015 06:54 AM, Dario Faggioli wrote:
>
>> > Yeah, well, sorry, but even if we both (me and George) encouraged
>> > you
>> > to try Credit2, that wasn't a great idea. :-(  In fact, you're
>> > using
>> > pinning for this test, and Credit2 does not have pinning (yet)! :-P
>> >
>> > That explains why utilizations are summing up to higher than 100%:
>> > vCPUs are just not being confined to one processor.
>> >
>> > Pinning for Credit2 is just around the corner. Let's try this again
>> > when it will be there, ok? :-D
>>
>> Or try it in a cpupool with just one pcpu?
>>
> Oh, well, yes. That is certainly an alternative. :-)
>
> I'm curious about how it'd go, so I'm probably going to give it a try
> later...

I was going to say, using cpupools rather than pinning is probably a
better idea anyway.  I might go so far as to say that if you're trying
to test the actual scheduling algorithms, you should *only* use
cpupools and *never* pinning.  The whole reason we invented cpupools
in the first place was that pinning tends to break the assumptions of
the scheduling algorithms in ways it's not really cost-effective to
work around.

 -George

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