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

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Tue, 2015-05-19 at 18:35 +0100, Wei Liu wrote:
> On Sat, May 16, 2015 at 03:15:21AM +0200, Dario Faggioli wrote:

> > > === 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?
> 
Sounds good, thanks.

Regards,
Dario

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