Re: [Qemu-discuss] VM tuning

[Stephan von Krawczynski]

Hi Peter,

I know the deadline stuff, this is already in. But the problem arises
nevertheless. My idea is that mv.dirty_ratio should be a lot higher to prevent
the lagging, probably around 80.

-- 
Regards,
Stephan




On Fri, 04 Oct 2013 08:46:49 -0700
Peter Kieser <address@hidden> wrote:

> Change your I/O scheduler to deadline from cfq. IBM has a KVM best 
> practices guide, which outlines the differences between the schedulers:
> 
> http://pic.dhe.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=%2Fliaat%2Fliaatbpdeadline.htm
> 
> -Peter
> 
> On 2013-10-04 4:07 AM, Stephan von Krawczynski wrote:
> > Hello all,
> >
> > I try to setup a box with 128GB and 32 cpus split into 2 numa nodes. I found
> > out that while copying a large file to the host some of the qemu guests 
> > start
> > choking. I guess this is because of the vm cache setup.
> > The probably most important two tunables are:
> >
> > vm.dirty_background_ratio = 10
> > vm.dirty_ratio = 20
> >
> > which is the ditros/kernels (3.11.2) standard setup.
> > Does anybody have a better idea about these for such a setup?
> > The guests mem sizes btw sum up to around half of the physical mem, the rest
> > is used as cache.
>