Re: [Xen-devel] Status of Credit2 and Credit1 [was: Re: Xen 4.6 Development Update (four months reminder)]

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Sat, May 16, 2015 at 03:15:21AM +0200, Dario Faggioli wrote:
> On Wed, 2015-05-13 at 06:01 +0100, wei.liu2@xxxxxxxxxx wrote:
> 
> > = Prognosis =
> > 
> > The states are: none -> fair -> ok -> good -> done
> > 
> > none - nothing yet
> > fair - still working on it, patches are prototypes or RFC
> > ok   - patches posted, acting on review
> > good - some last minute pieces
> > done - all done, might have bugs
> 
> > == Hypervisor == 
> 
> > *  Credit2 production ready (none)
> >    cpu reservation
> >   -  George Dunlap
> >
> No work on this yet, AFAIK. I may be able to look into it in a couple of
> weeks, but I still am not sure.
> 
> > === Hypervisor X86 === 
> 
> > *  HT enabled with credit has 7.9 per perf drop. (none)
> >    kernbench demonstrated it
> >    http://www.gossamer-threads.com/lists/xen/devel/339409
> >    This has existed since credit1 introduction.
> >   -  Dario Faggioli
> >
> Let me clarify this a bit.
> 
> First of all, let me point out that the issue only shows up in
> under-loaded systems (i.e., with less active vcPUs then the host has
> pCPUs). In any case, this is something inherent in Credit1 architecture,
> and I don't have a sensible idea on how to deal with it without causing
> other problems.
> 
> I am working on some improvement to Credit1 (e.g., introducing load
> tracking and basing some decisions on it), which hopefully will help
> better performance even in this case, but I'm not actively working on
> fixing this (if it can be fixed).
> 

I have moved this to deferred section. Is this OK?

Wei.

> Regards,
> Dario



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