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

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Tue, 2015-10-27 at 09:44 +0000, George Dunlap wrote:
> On Tue, Oct 27, 2015 at 5:59 AM, suokun <suokunstar@xxxxxxxxx> wrote:
> > Hi all,
> > 
> > The BOOST mechanism in Xen credit scheduler is designed to
> > prioritize
> > VM which has I/O-intensive application to handle the I/O request in
> > time. However, this does not always work as expected.
> 
> Thanks for the exploration, and the analysis.
> 
Yep, indeed. :-)

> The BOOST mechanism is part of the reason I began to write the
> credit2
> scheduler, which we are  hoping (any day now) to make the default
> scheduler.  It was designed specifically with the workload you
> mention
> in mind.  
>
The whole BOOST thing is an hack, and I don't have much problems
believing it interacts poorly with the tickling mechanism, which, in
Credit1, is not very precise and reliable (e.g., in Credit2, there is a
'tickled' mask).

That being said, I'm looking at the analysis itself, and I'm not sure I
understand what exactly you are suggesting it's going on... I will
reply shortly with a few questions.

> Would you care to try your test again and see how it fares?
> 
Well, that would be a lot useful, for sure! :-D

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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